Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust Aftertreatment

*Jon Ander Onrubia-Calvo, Beñat Pereda-Ayo, Unai De-La-Torre and Juan Ramón González-Velasco*

## **Abstract**

NOx removal is still a technological challenge in diesel engines. NOx storage and reduction (NSR), selective catalytic reduction (SCR), and combined NSR-SCR systems are the efficient approaches for diesel exhaust aftertreatment control. However, NSR and combined NSR-SCR technologies require high noble metal loadings, with low thermal stability and high cost. Recently, perovskites have gained special attention as an efficient alternative to substituting noble metals in heterogeneous catalysis. Up to date, few studies analyzed the application of perovskites in automobile catalytic converters. This chapter overviews recent research on development of novel perovskitebased catalysts as a component of single-NSR and hybrid NSR-SCR systems for NOx removal from diesel engine exhaust gases. Results in our laboratory are compared with similar work reported in the literature by other authors. Under realistic conditions, 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 catalyst achieves NOx-to-N2 conversion higher than 92% when is coupled with an SCR catalyst placed downstream. The results show promise for a considerably higher thermal stability and lower cost diesel exhaust treatment system.

**Keywords:** perovskite, Pt-free catalyst, NOx removal, lean-burn engine, NSR, NSR-SCR

## **1. Introduction**

Diesel and lean-burn engines operate with high air-to-fuel (A/F) ratios in the range of 20–65 depending on the design of the engine and the type of fuel being combusted. This environment leads to a better fuel economy, with lower CO2, CO, and HC emissions than stoichiometric gasoline engines (A/F~14.6). As a result, diesel and lean-burn engines gained popularity during the last decades, especially in Europe. However, operation under such net oxidizing environment makes three-way catalysts (TWC) not efficient enough to meet Euro VI standards regarding NOx emissions in those engines (**Table 1**). Furthermore, the production of particulate matter, also known as soot, is still unavoidable [1, 2]. As a result, diesel and lean-burn engines require the implementation of


*a Type approval test for HDVs is conducted on an engine dynamometer, and limits defined as mass emitted per unit of mechanical work done (g kW h<sup>−</sup><sup>1</sup> ).*

*b Type approval test for LDVs is conducted on an engine dynamometer, and limits defined as mass emitted per unit of distance driven (g km<sup>−</sup><sup>1</sup> ).*

*\*European Union heavy-duty engine emission standards are denoted by Roman numerals, while light-duty vehicle standards are denoted by Arabic numbers.*

#### **Table 1.**

*Evolution of Euro regulations for heavy-duty engines and passenger vehicles.*

aftertreatment systems to control pollutant emissions, especially those related to NOx and soot emission.

Current diesel engine exhaust treatment system can contain: (i) diesel oxidation catalyst (DOC); (ii) diesel particulate filter (DPF); (iii) NOx reduction catalyst; and (iv) ammonia slip catalyst (ASC) [3]. NOx storage and reduction (NSR) and selective catalytic reduction (SCR) technologies are the most promising approaches to control NOx emission [4]. NSR system, also known as lean NOx trap (LNT), operates cyclically under lean-rich periods with 1.5% Pt–15% BaO/Al2O3 as model catalyst. On the other hand, NH3-SCR systems are based on the selectively catalyzed reduction of NOx-to-N2 with externally added NH3 (produced by hydrolysis of urea) in an oxygen-rich environment. Cu or Fe/zeolite catalysts are the model NH3- SCR formulations [5]. Current status of these technologies has some drawbacks that are limiting their extended implementation.

During the last years, a reasonable interest in linking NSR and NH3-SCR systems is growing [6–9], because NSR systems generate NH3 as byproduct during the shortrich period, whereas this compound is the usual selective reducing agent in the SCR technology. As a result, NOx removal efficiency of the hybrid system increases notably with a simultaneous decrease in the NH3 slip. Hence, the combined NSR-SCR system is considered as a potential solution to overcome main limitations of the stand-alone NSR and stand-alone SCR technologies. The hybrid NSR-SCR technology consists of two catalysts (NSR and SCR) arranged in series or in a single brick, which runs cyclically similarly to single-NSR systems. Up to now, the behavior of hybrid LNT-SCR systems has been mainly verified with the model 1.5% Pt–15% BaO/Al2O3 NSR catalyst. As already mentioned, the presence of platinum makes this formulation costly and limits hydrothermal stability.

Libby [10] and Voorhoeve et al. [11] proposed firstly in early 1970s a perovskitebased catalyst for automotive applications. From then, several studies were carried out related to the utilization of perovskite-based catalysts in diesel exhaust control. The perovskite formulation corresponds to oxides with ABO3 and/or A2BO4 structure, where A is the larger cation located in the center edge of the structure and B is a smaller cation

**73**

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust…*

located in the center of the octahedron [12]. Specifically, A can be a lanthanide, alkaline, or alkaline-earth cation, and B cation can be any metallic element from 3, 4, or 5d configuration. One of the main advantages of the perovskite structure is the possibility to adopt a wide range of different compositions, changing either the A or the B cation or partially substituting each of them by other cations with same or different valences without destroying the perovskite structure. This leads to the formation of oxygen vacancies or changes in the oxidation state of A and B cations, allowing modulation of catalytic properties of the sample to better adapt to automotive applications [13]. All above in mind, the objective of this chapter is to provide a general outlook on utilization of perovskite-based formulations as stand-alone NSR catalysts as well as combined with a zeolite SCR catalyst to conform an efficient hybrid NSR-SCR system. First, a general overview of the application of perovskite-based formulations to control nitrogen oxide emissions from diesel engines is addressed. Then, the applicability of the perovskite-based formulation to single-NSR and combined NSR-SCR technologies will be emphasized. Special attention is paid to the promise and viability

of this type of materials as alternative to Pt-based NSR model catalysts.

**2. General overview on application of perovskite-based catalysts for NOx**

Perovskite oxides exhibit a range of stoichiometry and crystal structures. In fact, they could accommodate around 90% of the metallic natural elements of the periodic table. The A and Ba cations can be partially replaced inside the structure, allowing tailoring their catalytic properties to better adapt to their application. Furthermore, physicochemical properties can be controlled by the modification of preparation method. As a result, these materials have been widely implemented in heterogeneous catalysis. Moreover, their high-hydrothermal stability enables their

Many works suggest the application of perovskite oxides as alternative formulations to those based on platinum-group metals (PGMs) in automotive exhaust catalytic converters [10, 11, 14, 15]. This type of material has shown excellent activity in oxidation reaction working as diesel oxidation catalyst (DOC) [15–23]. Perovskite oxides demonstrated to be efficient for the simultaneous removal of NOx and soot combustion in diesel engines allowing their implementation in diesel particulate-NOx reduction filter (DPNR) [24–31]. Furthermore, NOx decomposition in the form of nitrous oxide or nitric oxide has been proposed as a one their potential applications [32–38]. Finally, these formulations have been widely implemented for NOx reduction in both stoichiometric gasoline engines (three-way catalyst, TWC) [24, 39–45] and diesel or lean-burn gasoline engines. Indeed, their implementation in the control of NOx emission from diesel engines has gained special attention during the last decades, both in the selective catalytic reduction (SCR) and in the NOx storage and reduction (NSR) systems.

SCR technology consists in the selective reduction of NOx by different reducing agents (NH3, H2, or HC) in a net oxidizing environment. The NH3-SCR alternative became as the most promising avenue for NOx control in diesel engines. This technology was initially implemented in stationary emission sources. However, their characteristics permit to adopt it for automobile applications. SCR technology runs under steady-state operation conditions with continuous admission of NH3 to stoichiometrically reduce NOx in an oxygen-rich environment. A urea tank is usually required for NH3 supply (by hydrolysis of urea) to achieve the SCR reactions. Due to the

application in catalytic processes carried out at high temperatures [12, 13].

*DOI: http://dx.doi.org/10.5772/intechopen.89532*

**emission control**

**2.1 Selective catalytic reduction (SCR)**

### *Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust… DOI: http://dx.doi.org/10.5772/intechopen.89532*

located in the center of the octahedron [12]. Specifically, A can be a lanthanide, alkaline, or alkaline-earth cation, and B cation can be any metallic element from 3, 4, or 5d configuration. One of the main advantages of the perovskite structure is the possibility to adopt a wide range of different compositions, changing either the A or the B cation or partially substituting each of them by other cations with same or different valences without destroying the perovskite structure. This leads to the formation of oxygen vacancies or changes in the oxidation state of A and B cations, allowing modulation of catalytic properties of the sample to better adapt to automotive applications [13].

All above in mind, the objective of this chapter is to provide a general outlook on utilization of perovskite-based formulations as stand-alone NSR catalysts as well as combined with a zeolite SCR catalyst to conform an efficient hybrid NSR-SCR system. First, a general overview of the application of perovskite-based formulations to control nitrogen oxide emissions from diesel engines is addressed. Then, the applicability of the perovskite-based formulation to single-NSR and combined NSR-SCR technologies will be emphasized. Special attention is paid to the promise and viability of this type of materials as alternative to Pt-based NSR model catalysts.

## **2. General overview on application of perovskite-based catalysts for NOx emission control**

Perovskite oxides exhibit a range of stoichiometry and crystal structures. In fact, they could accommodate around 90% of the metallic natural elements of the periodic table. The A and Ba cations can be partially replaced inside the structure, allowing tailoring their catalytic properties to better adapt to their application. Furthermore, physicochemical properties can be controlled by the modification of preparation method. As a result, these materials have been widely implemented in heterogeneous catalysis. Moreover, their high-hydrothermal stability enables their application in catalytic processes carried out at high temperatures [12, 13].

Many works suggest the application of perovskite oxides as alternative formulations to those based on platinum-group metals (PGMs) in automotive exhaust catalytic converters [10, 11, 14, 15]. This type of material has shown excellent activity in oxidation reaction working as diesel oxidation catalyst (DOC) [15–23]. Perovskite oxides demonstrated to be efficient for the simultaneous removal of NOx and soot combustion in diesel engines allowing their implementation in diesel particulate-NOx reduction filter (DPNR) [24–31]. Furthermore, NOx decomposition in the form of nitrous oxide or nitric oxide has been proposed as a one their potential applications [32–38]. Finally, these formulations have been widely implemented for NOx reduction in both stoichiometric gasoline engines (three-way catalyst, TWC) [24, 39–45] and diesel or lean-burn gasoline engines. Indeed, their implementation in the control of NOx emission from diesel engines has gained special attention during the last decades, both in the selective catalytic reduction (SCR) and in the NOx storage and reduction (NSR) systems.

## **2.1 Selective catalytic reduction (SCR)**

SCR technology consists in the selective reduction of NOx by different reducing agents (NH3, H2, or HC) in a net oxidizing environment. The NH3-SCR alternative became as the most promising avenue for NOx control in diesel engines. This technology was initially implemented in stationary emission sources. However, their characteristics permit to adopt it for automobile applications. SCR technology runs under steady-state operation conditions with continuous admission of NH3 to stoichiometrically reduce NOx in an oxygen-rich environment. A urea tank is usually required for NH3 supply (by hydrolysis of urea) to achieve the SCR reactions. Due to the

*Perovskite Materials, Devices and Integration*

**Euro level\* NOx emission** 

3/III 5

*).*

*Evolution of Euro regulations for heavy-duty engines and passenger vehicles.*

*).*

**limit**

**Year of implementation**

<sup>a</sup> 2000 DOC + DPF

1–3/I–III DOC

1–3/I–III DOC

3/III 0.5b 2001 DOC + DPF 4/IV 0.25b 2006 DOC + DPF 5/V 0.18b 2011 DOC + DPF + DeNOx 6/VI 0.08b 2015 DOC + DPF + DeNOx + ASC

4/IV 3.5a 2005 DOC + DPF 5/V 2a 2008 DOC + DPF + DeNOx 6/VI 0.4/0.46a 2014 DOC + DPF + DeNOx + ASC

**Aftertreatment system composition**

**Type of vehicle**

Heavy-duty engines

Passengers vehicles

*a*

*b*

**Table 1.**

NOx and soot emission.

*of mechanical work done (g kW h<sup>−</sup><sup>1</sup>*

*standards are denoted by Arabic numbers.*

*unit of distance driven (g km<sup>−</sup><sup>1</sup>*

are limiting their extended implementation.

formulation costly and limits hydrothermal stability.

aftertreatment systems to control pollutant emissions, especially those related to

*Type approval test for HDVs is conducted on an engine dynamometer, and limits defined as mass emitted per unit* 

*\*European Union heavy-duty engine emission standards are denoted by Roman numerals, while light-duty vehicle* 

*Type approval test for LDVs is conducted on an engine dynamometer, and limits defined as mass emitted per* 

Current diesel engine exhaust treatment system can contain: (i) diesel oxidation catalyst (DOC); (ii) diesel particulate filter (DPF); (iii) NOx reduction catalyst; and (iv) ammonia slip catalyst (ASC) [3]. NOx storage and reduction (NSR) and selective catalytic reduction (SCR) technologies are the most promising approaches to control NOx emission [4]. NSR system, also known as lean NOx trap (LNT), operates cyclically under lean-rich periods with 1.5% Pt–15% BaO/Al2O3 as model catalyst. On the other hand, NH3-SCR systems are based on the selectively catalyzed reduction of NOx-to-N2 with externally added NH3 (produced by hydrolysis of urea) in an oxygen-rich environment. Cu or Fe/zeolite catalysts are the model NH3- SCR formulations [5]. Current status of these technologies has some drawbacks that

During the last years, a reasonable interest in linking NSR and NH3-SCR systems is growing [6–9], because NSR systems generate NH3 as byproduct during the shortrich period, whereas this compound is the usual selective reducing agent in the SCR technology. As a result, NOx removal efficiency of the hybrid system increases notably with a simultaneous decrease in the NH3 slip. Hence, the combined NSR-SCR system is considered as a potential solution to overcome main limitations of the stand-alone NSR and stand-alone SCR technologies. The hybrid NSR-SCR technology consists of two catalysts (NSR and SCR) arranged in series or in a single brick, which runs cyclically similarly to single-NSR systems. Up to now, the behavior of hybrid LNT-SCR systems has been mainly verified with the model 1.5% Pt–15% BaO/Al2O3 NSR catalyst. As already mentioned, the presence of platinum makes this

Libby [10] and Voorhoeve et al. [11] proposed firstly in early 1970s a perovskitebased catalyst for automotive applications. From then, several studies were carried out related to the utilization of perovskite-based catalysts in diesel exhaust control. The perovskite formulation corresponds to oxides with ABO3 and/or A2BO4 structure, where A is the larger cation located in the center edge of the structure and B is a smaller cation

**72**

requirement of large space to house the urea tank, the implementation of this alternative is limited to heavy-duty vehicles. Another disadvantage is the need of a NH3-slip catalyst to avoid NH3 emission. Furthermore, the ammonia decomposition occurs above 180°C, which limits the NOx removal efficiency at low temperatures.

It is widely accepted [46–48] that the following three main reactions occur during NOx reduction through NH3-SCR: (i) standard SCR (4NH3 + 4NO + O2 → 4H2 + 6H2O); (ii) fast SCR (2NH3 + NO + NO2 → 2 N2 + 3H2O), and (iii) slow NO2 SCR (4NH3 + 3NO2 → 3.5 N2 + 6H2O). The extent of these reactions depends on the NO/NO2 ratio, which in turn is related to the oxidation capacity of the catalyst. NOx removal efficiency is favored with NO/NO2 ratio around 1 as promoting the fast SCR reaction [49] and occurring reaction at lower temperature. Nevertheless, side reactions such as NH3 oxidation, NO oxidation, or N2O formation from ammonium nitrate decomposition can also occur.

NH3-SCR formulations have evolved from vanadia-based catalysts, first adopted in stationary sources, to the current Cu or Fe supported over new nano-pore zeolites with chabazite-type structure, such as SSZ-13 or SAPO-34. These formulations have already been implemented for NOx emission control in heavy-duty vehicles and some recently in some passenger's cars in Europe, mainly due to high NOx removal efficiency in a wide temperature window discovered with this small pore zeolite structure.

**Figure 1** shows the NH3-SCR behavior of a 4% Cu/SAPO-34 prepared in our laboratory by the solid state ion exchange method [50]. Experiments were carried out with a feed stream composed of 660 ppm NO, 660 ppm NH3, 6% O2, and Ar to balance. NO conversion increased with temperature as the NH3-SCR reactions are promoted, reaching almost full conversion in an extended range from 200 to 350°C and decreasing afterward as the oxidation of ammonia with O2 is favored at higher temperatures [51]. NH3 conversion also increases with temperature, but 100% conversion was maintained above certain temperature where the NH3-O2 reaction prevails. Regarding selectivity toward N2 is around 95–100% below 350°C, whereas above this temperature, it starts to decrease due to the NH3 partial oxidation, which partially limits NOx NH3-SCR reactions. The excellent DeNOx activity of this formulation is attributed to the preferential presence of copper as isolated Cu2+ ions in the double six member rings (d6r)<sup>2</sup> ; however, the presence of CuO aggregates also plays an important role in the NO-to-NO2 conversion oxidation.

Alternative compounds have been investigated for NH3-SCR technology, such as supported metal oxides (MnOx/Al2O3 and V2O5/activated carbon) [52–54], mixed oxides derived from hydrotalcite compounds such as Cu-Mg-Al [55], and perovskites oxides. Most of the catalytic studies related to the utilization of perovskite-type compositions in DeNOx technologies are based on La as A cation. However, few of them are related to NH3-SCR technology, being focused most of them on a great majority on H2-SCR and HC-SCR alternatives [3]. The NOx removal efficiency of LaMnO3, LaMn0.95V0.05O3, and BiMnO3 perovskites was analyzed [56–58]. Among them, BiMnO3 perovskite achieved higher NH3-SCR activity at lower temperatures. LaMnO3/attapulguite [59] and Fe-containing perovskites [57, 60] (LaMn0.95Fe0.05O3, LaCo0.3Fe0.7O3, or La0.8Sr0.2Fe1−xRhxO3) were also analyzed. However, these formulations showed limited NOx conversion (70–90%) or selectivity toward N2. Taking into account the results observed in **Figure 1**, these formulations still not represent a real alternative to current Cu/chabazite NH3-SCR catalysts.

## **2.2 NOx storage and reduction (NSR)**

The NSR concept, also known as lean NOx trap (LNT), was pioneered by Toyota in the middle 1990s [61]. In this technology, the engine works predominantly feeding a fuel-lean mixture with periodical short-rich excursions. During the lean

**75**

**Figure 1.**

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust…*

period, the NO is oxidized to NO2 and then adsorbed over the catalyst in the form of nitrites and specially nitrates up to its saturation. Then, the stored NOx should be released and reduced by a reductant, such as CO, H2, or HC, during the short-rich period. The operational principle addressed the choice of NSR catalyst composition, which usually contains platinum group metals (e.g. Pt, Pd, and Rh) to activate NO oxidation and NOx reduction and an alkaline or alkaline earth metal (e.g. K, Ba, Ca, and Sr) to promote NOx adsorption during lean conditions. Both metals are well distributed over high-surface area materials as alumina, ceria, zirconia, or mixed oxides. A composition consisting of (1–2%) Pt/(10–15%) BaO/Al2O3 is widely accepted as the model NSR formulation [62–65]. **Figure 2** shows the typical NOx storage and reduction operational principle on the NSR model catalyst [66].

*Evolution of NO conversion (a), ammonia conversion (b), and selectivity toward nitrogen, nitrogen dioxide, and nitrous oxide with reaction temperature, achieved with 4% Cu/SAPO-34 catalyst. Feed: 660 ppm NO,* 

*.*

*660 ppm NH3, 6% O2, Ar to balance; W/FA0 = 222 (g cat.) h Mol<sup>−</sup><sup>1</sup>*

LNT system shows some drawbacks derived from the operation principle and model formulation composition. On the one hand, LNT system shows NOx leak due

*DOI: http://dx.doi.org/10.5772/intechopen.89532*

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust… DOI: http://dx.doi.org/10.5772/intechopen.89532*

**Figure 1.**

*Perovskite Materials, Devices and Integration*

in the double six member rings (d6r)<sup>2</sup>

**2.2 NOx storage and reduction (NSR)**

tion can also occur.

requirement of large space to house the urea tank, the implementation of this alternative is limited to heavy-duty vehicles. Another disadvantage is the need of a NH3-slip catalyst to avoid NH3 emission. Furthermore, the ammonia decomposition occurs above 180°C, which limits the NOx removal efficiency at low temperatures.

It is widely accepted [46–48] that the following three main reactions occur during NOx reduction through NH3-SCR: (i) standard SCR (4NH3 + 4NO + O2 → 4H2 + 6H2O);

(4NH3 + 3NO2 → 3.5 N2 + 6H2O). The extent of these reactions depends on the NO/NO2 ratio, which in turn is related to the oxidation capacity of the catalyst. NOx removal efficiency is favored with NO/NO2 ratio around 1 as promoting the fast SCR reaction [49] and occurring reaction at lower temperature. Nevertheless, side reactions such as NH3 oxidation, NO oxidation, or N2O formation from ammonium nitrate decomposi-

NH3-SCR formulations have evolved from vanadia-based catalysts, first adopted in stationary sources, to the current Cu or Fe supported over new nano-pore zeolites with chabazite-type structure, such as SSZ-13 or SAPO-34. These formulations have already been implemented for NOx emission control in heavy-duty vehicles and some recently in some passenger's cars in Europe, mainly due to high NOx removal efficiency in a wide temperature window discovered with this small pore zeolite structure.

**Figure 1** shows the NH3-SCR behavior of a 4% Cu/SAPO-34 prepared in our laboratory by the solid state ion exchange method [50]. Experiments were carried out with a feed stream composed of 660 ppm NO, 660 ppm NH3, 6% O2, and Ar to balance. NO conversion increased with temperature as the NH3-SCR reactions are promoted, reaching almost full conversion in an extended range from 200 to 350°C and decreasing afterward as the oxidation of ammonia with O2 is favored at higher temperatures [51]. NH3 conversion also increases with temperature, but 100% conversion was maintained above certain temperature where the NH3-O2 reaction prevails. Regarding selectivity toward N2 is around 95–100% below 350°C, whereas above this temperature, it starts to decrease due to the NH3 partial oxidation, which partially limits NOx NH3-SCR reactions. The excellent DeNOx activity of this formulation is attributed to the preferential presence of copper as isolated Cu2+ ions

Alternative compounds have been investigated for NH3-SCR technology, such as supported metal oxides (MnOx/Al2O3 and V2O5/activated carbon) [52–54], mixed oxides derived from hydrotalcite compounds such as Cu-Mg-Al [55], and perovskites oxides. Most of the catalytic studies related to the utilization of perovskite-type compositions in DeNOx technologies are based on La as A cation. However, few of them are related to NH3-SCR technology, being focused most of them on a great majority on H2-SCR and HC-SCR alternatives [3]. The NOx removal efficiency of LaMnO3, LaMn0.95V0.05O3, and BiMnO3 perovskites was analyzed [56–58]. Among them, BiMnO3 perovskite achieved higher NH3-SCR activity at lower temperatures. LaMnO3/attapulguite [59] and Fe-containing perovskites [57, 60] (LaMn0.95Fe0.05O3, LaCo0.3Fe0.7O3, or La0.8Sr0.2Fe1−xRhxO3) were also analyzed. However, these formulations showed limited NOx conversion (70–90%) or selectivity toward N2. Taking into account the results observed in **Figure 1**, these formulations still not represent a

The NSR concept, also known as lean NOx trap (LNT), was pioneered by Toyota

in the middle 1990s [61]. In this technology, the engine works predominantly feeding a fuel-lean mixture with periodical short-rich excursions. During the lean

also plays an important role in the NO-to-NO2 conversion oxidation.

real alternative to current Cu/chabazite NH3-SCR catalysts.

; however, the presence of CuO aggregates

(ii) fast SCR (2NH3 + NO + NO2 → 2 N2 + 3H2O), and (iii) slow NO2 SCR

**74**

*Evolution of NO conversion (a), ammonia conversion (b), and selectivity toward nitrogen, nitrogen dioxide, and nitrous oxide with reaction temperature, achieved with 4% Cu/SAPO-34 catalyst. Feed: 660 ppm NO, 660 ppm NH3, 6% O2, Ar to balance; W/FA0 = 222 (g cat.) h Mol<sup>−</sup><sup>1</sup> .*

period, the NO is oxidized to NO2 and then adsorbed over the catalyst in the form of nitrites and specially nitrates up to its saturation. Then, the stored NOx should be released and reduced by a reductant, such as CO, H2, or HC, during the short-rich period. The operational principle addressed the choice of NSR catalyst composition, which usually contains platinum group metals (e.g. Pt, Pd, and Rh) to activate NO oxidation and NOx reduction and an alkaline or alkaline earth metal (e.g. K, Ba, Ca, and Sr) to promote NOx adsorption during lean conditions. Both metals are well distributed over high-surface area materials as alumina, ceria, zirconia, or mixed oxides. A composition consisting of (1–2%) Pt/(10–15%) BaO/Al2O3 is widely accepted as the model NSR formulation [62–65]. **Figure 2** shows the typical NOx storage and reduction operational principle on the NSR model catalyst [66].

LNT system shows some drawbacks derived from the operation principle and model formulation composition. On the one hand, LNT system shows NOx leak due

#### **Figure 2.**

*NOx storage and reduction: mechanism (upper figure), NOx outlet concentration during three consecutive lean-rich cycles (bottom figure).*

to the dynamic operation conditions under lean-rich conditions, and large amounts of N2O and NH3 can be also formed during rich period [67]. Furthermore, the catalyst requires high Pt loading to promote NO-to-NO2 oxidation, which increases the cost and decreases thermal stability. Finally, the resistance to sulfur poisoning is also limited. Thus, the application of NSR technology is limited to light-duty vehicles with lean-burn engines using low-sulfur containing fuels [3].

During the last decades, modifications in composition of NSR model catalyst and new formulations such as perovskite-based materials have been explored with enhanced catalytic properties, strong deactivation resistance, and lower cost.

The application of perovskites to NSR application is mainly based on high capacity of this material to adsorb NOx during the lean period. NO-to-NO2 oxidation is considered a primary step for NOx adsorption via nitrates in the model NSR catalyst, on which NO2 adsorbs much faster than NO. With model NSR catalyst, this requires high Pt loads, which drastically increases the cost and limits the thermal stability [68, 69]. Many authors focused on development of perovskite-based formulations with high NO oxidation capacity as promising materials for use in automobile applications. In this sense, perovskite structures (ABO3) such as LaCoO3 and LaMnO3 showed excellent performance on oxidation reactions [70, 71]. Choi et al. [72] reported that the catalytic oxidation activity is intimately connected to molecular and atomic interactions of oxygen with the oxide surface. Catalytic oxidation over metal oxides (M) is often rationalized in terms of a Mars-van Krevelen mechanism [73, 74], in which vacancies (□) in the oxide lattice facilitate the adsorption and dissociation of O2.

$$\mathcal{Z}(\!\!\!-\!\!M\!-\!\!\!\!-\!\!\!\!D-\!\!\!M\!-\!\!\!\!\!\/)\!+\mathcal{O}\_{2}\rightarrow\mathcal{Z}(\!\!\!-\!\!M\!-\!\!\!\!M\!-\!\!\!\!\!\!\/)\tag{1}$$

Subsequent reaction with a reductant (R) reforms the vacancies to complete the catalytic cycle.

$$\text{R} + (\text{--M---O--M---}) \rightarrow (\text{--R---O}) + (\text{--M---D--M--}) \tag{2}$$

**77**

approach.

**Figure 3.**

*Elsevier).*

on the surface [16].

automotive catalysis.

g<sup>−</sup><sup>1</sup>

(around 20 m2

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust…*

As a result, perovskite activity for oxidation reactions seems to be related to a change in the oxidation state of B cation, active oxygen mobility, and ion vacancy defect [70]. The enhancement of oxidation activity of perovskite-based catalysts is usually attributed to a promotion of oxygen vacancy density [75–79]. In this sense, lanthanum partial substitution by other cations modifies the composition and alters the physico-chemical properties of perovskite, such as crystallinity, specific surface area, average crystal size, abundance of oxygen vacancies, and oxidation state of B cation. Among different cations, Sr2+ seems to be the most promising cation for this

*Evolution of α desorbed oxygen species and NO-to-NO2 conversion at 300°C with lanthanum substitution degree for (a) La1−xSrxCoO3 and (b) La1−xSrxMnO3 perovskites (reprinted from Ref. [16] with permission of* 

**Figure 3** shows the evolution of α oxygen species concentration and NO-to-NO2

As a general trend, Sr promotes in a higher degree the formation of α oxygen species and NO-to-NO2 oxidation capacity for Co-based perovskites than for Mn ones. The evolution of NO-to-NO2 conversion with lanthanum substitution degree confirms that the amount of oxygen vacancies is the key factor for this enhancement. As a result, Co-based perovskites show higher NO oxidation capacity, even above than Pt-based catalyst does [16]. These results confirm that perovskites can be considered as an excellent alternative for promotion NO oxidation reactions in

Nonetheless, La0.7Sr0.3CoO3 tends to agglomerate under high temperatures required during the calcination step (**Figure 4**). Thus, low specific surface areas

as main drawbacks of bulk perovskites. Two approaches have been proposed to overcome this limitation: synthesizing mesostructured perovskites via nanocasting and/or distribution of perovskite over high-surface area materials [12]. Mesoporous supports were tried in the past. In this sense, overlaying ZrTiO4 with LaCoO3 perovskite was found to reduce sintering of perovskite, which improves NOx storage capacity [82]. More recently, You et al. [83, 84] found that ceria-supported and Ce0.75Zr0.25O2-supported LaCoO3 perovskite achieved high NOx storage and

analyzed the effect of incorporating increasing loadings of La0.7Sr0.3CoO3 perovskite

over a conventional alumina support [85], which inhibited crystal growth of

reduction capacity even with low-specific surface area (below 50 m<sup>2</sup>

) and an insufficient number of NOx storage sites [80, 81] arise

g<sup>−</sup><sup>1</sup>

). We

conversion at 300°C with degree of lanthanum substitution by Sr, for (a) La1−*<sup>x</sup>*Sr*x*CoO3 and (**Figure 3a**) La1−*<sup>x</sup>*Sr*x*MnO3 perovskites (**Figure 3b**). Note that α-oxygen was assigned to the oxygen release from vacancies located very near to or

*DOI: http://dx.doi.org/10.5772/intechopen.89532*

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust… DOI: http://dx.doi.org/10.5772/intechopen.89532*

**Figure 3.**

*Perovskite Materials, Devices and Integration*

to the dynamic operation conditions under lean-rich conditions, and large amounts of N2O and NH3 can be also formed during rich period [67]. Furthermore, the catalyst requires high Pt loading to promote NO-to-NO2 oxidation, which increases the cost and decreases thermal stability. Finally, the resistance to sulfur poisoning is also limited. Thus, the application of NSR technology is limited to light-duty

*NOx storage and reduction: mechanism (upper figure), NOx outlet concentration during three consecutive* 

During the last decades, modifications in composition of NSR model catalyst and new formulations such as perovskite-based materials have been explored with enhanced catalytic properties, strong deactivation resistance, and lower cost. The application of perovskites to NSR application is mainly based on high capacity of this material to adsorb NOx during the lean period. NO-to-NO2 oxidation is considered a primary step for NOx adsorption via nitrates in the model NSR catalyst, on which NO2 adsorbs much faster than NO. With model NSR catalyst, this requires high Pt loads, which drastically increases the cost and limits the thermal stability [68, 69]. Many authors focused on development of perovskite-based formulations with high NO oxidation capacity as promising materials for use in automobile applications. In this sense, perovskite structures (ABO3) such as LaCoO3 and LaMnO3 showed excellent performance on oxidation reactions [70, 71]. Choi et al. [72] reported that the catalytic oxidation activity is intimately connected to molecular and atomic interactions of oxygen with the oxide surface. Catalytic oxidation over metal oxides (M) is often rationalized in terms of a Mars-van Krevelen mechanism [73, 74], in which vacancies (□) in the oxide lattice facilitate

2(—M—□—M—) + O2 → 2(—M—O—M—) (1)

R + (—M—O—M—) → (—R—O) + (—M—□—M—) (2)

Subsequent reaction with a reductant (R) reforms the vacancies to complete the

vehicles with lean-burn engines using low-sulfur containing fuels [3].

**76**

catalytic cycle.

**Figure 2.**

*lean-rich cycles (bottom figure).*

the adsorption and dissociation of O2.

*Evolution of α desorbed oxygen species and NO-to-NO2 conversion at 300°C with lanthanum substitution degree for (a) La1−xSrxCoO3 and (b) La1−xSrxMnO3 perovskites (reprinted from Ref. [16] with permission of Elsevier).*

As a result, perovskite activity for oxidation reactions seems to be related to a change in the oxidation state of B cation, active oxygen mobility, and ion vacancy defect [70]. The enhancement of oxidation activity of perovskite-based catalysts is usually attributed to a promotion of oxygen vacancy density [75–79]. In this sense, lanthanum partial substitution by other cations modifies the composition and alters the physico-chemical properties of perovskite, such as crystallinity, specific surface area, average crystal size, abundance of oxygen vacancies, and oxidation state of B cation. Among different cations, Sr2+ seems to be the most promising cation for this approach.

**Figure 3** shows the evolution of α oxygen species concentration and NO-to-NO2 conversion at 300°C with degree of lanthanum substitution by Sr, for (a) La1−*<sup>x</sup>*Sr*x*CoO3 and (**Figure 3a**) La1−*<sup>x</sup>*Sr*x*MnO3 perovskites (**Figure 3b**). Note that α-oxygen was assigned to the oxygen release from vacancies located very near to or on the surface [16].

As a general trend, Sr promotes in a higher degree the formation of α oxygen species and NO-to-NO2 oxidation capacity for Co-based perovskites than for Mn ones. The evolution of NO-to-NO2 conversion with lanthanum substitution degree confirms that the amount of oxygen vacancies is the key factor for this enhancement. As a result, Co-based perovskites show higher NO oxidation capacity, even above than Pt-based catalyst does [16]. These results confirm that perovskites can be considered as an excellent alternative for promotion NO oxidation reactions in automotive catalysis.

Nonetheless, La0.7Sr0.3CoO3 tends to agglomerate under high temperatures required during the calcination step (**Figure 4**). Thus, low specific surface areas (around 20 m2 g<sup>−</sup><sup>1</sup> ) and an insufficient number of NOx storage sites [80, 81] arise as main drawbacks of bulk perovskites. Two approaches have been proposed to overcome this limitation: synthesizing mesostructured perovskites via nanocasting and/or distribution of perovskite over high-surface area materials [12]. Mesoporous supports were tried in the past. In this sense, overlaying ZrTiO4 with LaCoO3 perovskite was found to reduce sintering of perovskite, which improves NOx storage capacity [82]. More recently, You et al. [83, 84] found that ceria-supported and Ce0.75Zr0.25O2-supported LaCoO3 perovskite achieved high NOx storage and reduction capacity even with low-specific surface area (below 50 m<sup>2</sup> g<sup>−</sup><sup>1</sup> ). We analyzed the effect of incorporating increasing loadings of La0.7Sr0.3CoO3 perovskite over a conventional alumina support [85], which inhibited crystal growth of

#### **Figure 4.**

*TEM images of: (a) La0.7Sr0.3CoO3 and (b) 30% La0.7Sr0.3CoO3/Al2O3 samples (reprinted from Ref. [85] with permission of Elsevier).*

bulk perovskites (**Figure 4**). Hence, diffusion of intermediate compounds from oxidation to adsorption sites was facilitated. Among all prepared catalysts, 30% La0.7Sr0.3CoO3/Al2O3 sample achieved the most efficient use of perovskite phase due to the best balance between well-developed perovskite phase and NO oxidation and NO adsorption site distribution such as oxygen vacancies, structural La and Sr at the surface, and segregated SrCO3 [86, 87].

However, NOx reduction capacity of supported formulations is still limited (**Figure 5**). The incorporation of Pd is analyzed as a promising avenue to improve the NOx reduction capacity of the 30% La0.7Sr0.3CoO3/Al2O3 catalyst. Two approaches can be used for the incorporation of palladium in the perovskite-based formulations via impregnation [88–90] and/or by doping the perovskite structure [86, 91, 92]. The former promotes palladium accessibility; meanwhile, the latter seems to prevent the metal from agglomeration during reduction steps [93, 94]. However, contradictory conclusions have been extracted about which of them is the optimum alternative [95, 96]. In a recent study, Zhao et al. [97] compared both Pd incorporation methods for La0.7Sr0.3CoO3 perovskite. In their study, NOx adsorption during lean conditions and NOx reduction to N2 during rich period is significantly promoted after the incorporation of Pd, especially by impregnation method. The enhancement of the catalytic performance is related to a higher NOx adsorption site regeneration and to a promotion of NOx reduction rate by the palladium incorporation, respectively. In our previous work, we prepared several catalysts with increasing palladium contents (0.75, 1.5, and 3.0%) incorporated doping perovskite structure or by wetness impregnation over alumina-supported perovskite. They concluded that the 1.5% Pd–30% La0.7Sr0.3CoO3/Al2O3 sample shows the best balance between NOx removal efficiency and minimum palladium content. The NOx removal efficiency and nitrogen production are as high as 86.2 and 69.5%, respectively (**Figure 5**). DeNOx activity of this formulation is similar or even higher than that achieved with the reference catalyst (1.5% Pt–15% BaO/Al2O3). Thus, the developed formulation revealed as a promising alternative to the NSR model catalyst for NOx removal in the automotive application.

It is worth noting that proposed alternative showed a high NO2 outlet concentration under oxidizing conditions [66]. This suggests that on these materials more amount of NO2 is formed than the catalyst can adsorb during the lean period.

**79**

**Figure 5.**

*FA0 = 200 (g cat.) h Mol<sup>−</sup><sup>1</sup>*

*.*

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust…*

Furthermore, the amount of NOx released during the rich period denotes low stability of adsorbed species, which induces fast NOx release when the reductant is injected. Thus, NOx reduction, and as a consequence N2 production, could be further promoted. The increase of the concentration and strength of NOx adsorption sites by controlling an adequate balance between NO oxidation capacity and NOx adsorption site concentration and strength at the surface [80, 81] could be an alternative to overcome observed limitations. Two alternatives have been explored: (i) incorporation of additional NOx adsorption sites [82–84, 98, 99] and (ii) modification of perovskite composition to alter the nature and surface concentration of NOx adsorption sites [86, 100, 101]. The reported results show that the increase in NOx adsorption site concentration promotes NOx storage capacity confirming that the gas/solid equilibrium between NO2 and the available NOx adsorption sites is a key factor to maximize *NSC*; meanwhile, the higher strength of adsorber species favors NOx reduction efficiencies during short-rich period. Thus, both alternatives improved the catalytic behavior of the corresponding perovskite-based formulation. In our case, the selected approach was the modification of the perovskite composition by Ba doping instead of Sr doping. The developed formulation 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 adsorbs NOx in the form of nitrites/nitrates over surface basic sites, such as La or Ba-terminated perovskite surface, segregated BaCO3, or alumina support during lean conditions. Then, adsorbed NOx is released and reduced over Pd and in lower extent perovskite sites to form nitrogen containing products, such as N2O, NH3, or N2. Furthermore, a slower reaction of the NH3 formed with the stored nitrates leading to the selective formation of N2 also takes place [66].

*NO-to-NO2 conversion (XNO-to-NO2, first column), NOx storage capacity (NSC, second column), global NOx conversion (XNOx, third column), and nitrogen production (YN2, fourth column) at 400°C for perovskite-based formulations and NSR model catalyst. Feed: 500 ppm NO, 6% O2 (lean)/3% H2 (rich), Ar to balance; W/*

A critical aspect of NSR model catalyst (1.5% Pt–15% BaO/Al2O3) is the low sulfur resistance due to the formation of stable barium sulfate, which limits NOx

*DOI: http://dx.doi.org/10.5772/intechopen.89532*

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust… DOI: http://dx.doi.org/10.5772/intechopen.89532*

**Figure 5.**

*Perovskite Materials, Devices and Integration*

the surface, and segregated SrCO3 [86, 87].

**Figure 4.**

*permission of Elsevier).*

catalyst for NOx removal in the automotive application.

bulk perovskites (**Figure 4**). Hence, diffusion of intermediate compounds from oxidation to adsorption sites was facilitated. Among all prepared catalysts, 30% La0.7Sr0.3CoO3/Al2O3 sample achieved the most efficient use of perovskite phase due to the best balance between well-developed perovskite phase and NO oxidation and NO adsorption site distribution such as oxygen vacancies, structural La and Sr at

*TEM images of: (a) La0.7Sr0.3CoO3 and (b) 30% La0.7Sr0.3CoO3/Al2O3 samples (reprinted from Ref. [85] with* 

However, NOx reduction capacity of supported formulations is still limited (**Figure 5**). The incorporation of Pd is analyzed as a promising avenue to improve

approaches can be used for the incorporation of palladium in the perovskite-based formulations via impregnation [88–90] and/or by doping the perovskite structure [86, 91, 92]. The former promotes palladium accessibility; meanwhile, the latter seems to prevent the metal from agglomeration during reduction steps [93, 94]. However, contradictory conclusions have been extracted about which of them is the optimum alternative [95, 96]. In a recent study, Zhao et al. [97] compared both Pd incorporation methods for La0.7Sr0.3CoO3 perovskite. In their study, NOx adsorption during lean conditions and NOx reduction to N2 during rich period is significantly promoted after the incorporation of Pd, especially by impregnation method. The enhancement of the catalytic performance is related to a higher NOx adsorption site regeneration and to a promotion of NOx reduction rate by the palladium incorporation, respectively. In our previous work, we prepared several catalysts with increasing palladium contents (0.75, 1.5, and 3.0%) incorporated doping perovskite structure or by wetness impregnation over alumina-supported perovskite. They concluded that the 1.5% Pd–30% La0.7Sr0.3CoO3/Al2O3 sample shows the best balance between NOx removal efficiency and minimum palladium content. The NOx removal efficiency and nitrogen production are as high as 86.2 and 69.5%, respectively (**Figure 5**). DeNOx activity of this formulation is similar or even higher than that achieved with the reference catalyst (1.5% Pt–15% BaO/Al2O3). Thus, the developed formulation revealed as a promising alternative to the NSR model

It is worth noting that proposed alternative showed a high NO2 outlet concentration under oxidizing conditions [66]. This suggests that on these materials more amount of NO2 is formed than the catalyst can adsorb during the lean period.

the NOx reduction capacity of the 30% La0.7Sr0.3CoO3/Al2O3 catalyst. Two

**78**

*NO-to-NO2 conversion (XNO-to-NO2, first column), NOx storage capacity (NSC, second column), global NOx conversion (XNOx, third column), and nitrogen production (YN2, fourth column) at 400°C for perovskite-based formulations and NSR model catalyst. Feed: 500 ppm NO, 6% O2 (lean)/3% H2 (rich), Ar to balance; W/ FA0 = 200 (g cat.) h Mol<sup>−</sup><sup>1</sup> .*

Furthermore, the amount of NOx released during the rich period denotes low stability of adsorbed species, which induces fast NOx release when the reductant is injected. Thus, NOx reduction, and as a consequence N2 production, could be further promoted. The increase of the concentration and strength of NOx adsorption sites by controlling an adequate balance between NO oxidation capacity and NOx adsorption site concentration and strength at the surface [80, 81] could be an alternative to overcome observed limitations. Two alternatives have been explored: (i) incorporation of additional NOx adsorption sites [82–84, 98, 99] and (ii) modification of perovskite composition to alter the nature and surface concentration of NOx adsorption sites [86, 100, 101]. The reported results show that the increase in NOx adsorption site concentration promotes NOx storage capacity confirming that the gas/solid equilibrium between NO2 and the available NOx adsorption sites is a key factor to maximize *NSC*; meanwhile, the higher strength of adsorber species favors NOx reduction efficiencies during short-rich period. Thus, both alternatives improved the catalytic behavior of the corresponding perovskite-based formulation. In our case, the selected approach was the modification of the perovskite composition by Ba doping instead of Sr doping. The developed formulation 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 adsorbs NOx in the form of nitrites/nitrates over surface basic sites, such as La or Ba-terminated perovskite surface, segregated BaCO3, or alumina support during lean conditions. Then, adsorbed NOx is released and reduced over Pd and in lower extent perovskite sites to form nitrogen containing products, such as N2O, NH3, or N2. Furthermore, a slower reaction of the NH3 formed with the stored nitrates leading to the selective formation of N2 also takes place [66].

A critical aspect of NSR model catalyst (1.5% Pt–15% BaO/Al2O3) is the low sulfur resistance due to the formation of stable barium sulfate, which limits NOx adsorption during lean conditions. Hodjati et al. [102] analyzed NOx storage performance of ABO3 perovskite-type catalysts (with A = Ca, Sr, or Ba; and B = Sn, Zr, or Ti). Regarding A-site cations, the NOx storage capacity (*NSC*) followed the order Ba > Sr > Ca, whereas in the case of B cation, the order was Sn > Zr > Ti. Nevertheless, the BaSnO3 formulation exhibited limited sulfur resistance. In this sense, a BaFeO3 catalyst developed latter by Xian et al. [87, 103, 104] showed a lower decrease of *NSC* after sulfating (about 11–12%). The incorporation of Ti improves sulfur resistance in a higher extent; activity decreased only 5.1% after SO2-pretreatment of a BaFe1−*x*Ti*x*O3 catalyst (*x* = 0.1 or 0.2).

In the case of La-based perovskites, LaCo0.92Pt0.08O3 maintained a high NOx removal efficiency after regeneration of a pre-sulfated sample [105]. La0.7Sr0.3 Co0.8Fe0.2O3 perovskite suffers from a drop in NOx removal efficiency after SO2-pretreatment of 6.4% [106]. Wang et al. [107] and Wen et al. [99] compared the sulfur and hydrothermal aging resistance of LaCo0,92Pt0,08O3 and 0.3% Pt/ (Al2O3 + LaCoO3) catalysts, with respect to those shown by 1% Pt–16% Ba/Al2O3 model formulation. These alternatives achieved NOx-to-N2 reduction, sulfur resistance, regeneration, and durability similar or even higher than the model catalyst.

In summary, perovskite-based formulations achieve notable NO oxidation and NOx adsorption during oxidizing conditions. Furthermore, despite the fact that only a few works analyzed NOx removal during the short reducing period, our results summarized in this chapter remark the potential of perovskite-based materials for application in NOx storage and reduction (NSR) technology for NOx control in diesel and lean-burn engines. In fact, the excellent sulfur tolerance and hydrothermal resistance reported in previous work make these formulations even more promising alternative to Pt-based NSR model catalyst.

### **2.3 NSR-SCR combined system**

As previously observed, stand-alone SCR and NSR systems have some disadvantages that hinder their extended application in both light-duty and heavy-duty vehicles. In the case of the NSR system the high cost, poor thermal stability due to the use of precious metals and nondesired byproduct generation is the main disadvantages, whereas SCR systems require an urea system to provide NH3 and additional device to avoid ammonia slip under transient vehicle operation. The coupling of NSR and SCR catalysts has been rapidly accepted as a potential solution, since its discovery by the Ford Motor company [9, 108]. Different catalytic formulations, system architectures, and operation control have been explored [7, 8, 50, 109, 110]. The systems based on model NSR formulation and Cu/chabazite-type zeolites emerge as the most efficient combination [111]. This hybrid technology has been demonstrated more efficient by maximizing NOx-to-N2 reduction and minimizing NH3 slip with respect to the alone-NSR catalyst. Nevertheless, the most studied NSR formulation used in the combined NSR-SCR system has usually been the conventional Pt-based model catalyst (1.5% Pt-15% BaO/Al2O3), which transfers its high cost and limited hydrothermal stability to the hybrid configuration. Based on the results demonstrated by perovskite-based formulations in the single-NSR technology, their application in combined NSR-SCR systems is considered as an evolution of the current NSR-SCR architecture.

**Figure 6** shows the NOx (NO+NO2), N2O, and NH3 concentration profiles determined by FTIR for the single-NSR and double NSR-SCR configurations at 300°C. The N2 signal determined by mass spectroscopy is also included. NSR and SCR formulations correspond to 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 and 4% Cu/ SAPO-34 catalysts, respectively.

**81**

**Figure 6.**

the SCR, leading to further NOx reduction [114].

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust…*

The single-NSR system (**Figure 6a**) shows the typical NOx outlet concentration profile [112]. At the beginning of the lean period, practically all NOx fed are stored, and therefore, concentration of NOx at the reactor outlet is almost null. Then, as the length of the lean period increases, NOx adsorption sites become progressively saturated and NOx outlet concentration increases. In the subsequent rich period, H2 injected releases the stored NOx release and reduces it to a mixture of N2, NH3 and N2O [113]. During this period, the NH3 outlet concentration peaks to almost 1000 ppm (**Figure 6b**). NOx outlet concentration (**Figure 6a**) decreases drastically when the system operates under the NSR-SCR double configuration. As can be observed in **Figure 6b**, most NH3 formed during regeneration of the NSR catalyst is adsorbed on acidic sites of SAPO-34, since concentration of NH3 detected at the outlet of the combined NSR-SCR system is almost zero. Then, in the subsequent lean period, NOx slipping the NSR catalyst reacts with NH3 previously adsorbed on

*).*

*NOx (NO + NO2) and NH3 outlet concentrations, and MS signal of N2 for the single NSR and NSR-SCR configurations at 300°C. Feed: 500 ppm NO, 6% O2/3% H2, and Ar to balance; W/FA0 = 200 (g h Mol<sup>−</sup><sup>1</sup>*

The evolution of N2 signal also confirms the existence of SCR reaction over the Cu/SAPO-34 catalyst (**Figure 6c**). When the operation is performed with alone-NSR

*DOI: http://dx.doi.org/10.5772/intechopen.89532*

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust… DOI: http://dx.doi.org/10.5772/intechopen.89532*

**Figure 6.**

*Perovskite Materials, Devices and Integration*

a BaFe1−*x*Ti*x*O3 catalyst (*x* = 0.1 or 0.2).

**2.3 NSR-SCR combined system**

catalyst.

adsorption during lean conditions. Hodjati et al. [102] analyzed NOx storage performance of ABO3 perovskite-type catalysts (with A = Ca, Sr, or Ba; and B = Sn, Zr, or Ti). Regarding A-site cations, the NOx storage capacity (*NSC*) followed the order Ba > Sr > Ca, whereas in the case of B cation, the order was Sn > Zr > Ti. Nevertheless, the BaSnO3 formulation exhibited limited sulfur resistance. In this sense, a BaFeO3 catalyst developed latter by Xian et al. [87, 103, 104] showed a lower decrease of *NSC* after sulfating (about 11–12%). The incorporation of Ti improves sulfur resistance in a higher extent; activity decreased only 5.1% after SO2-pretreatment of

In the case of La-based perovskites, LaCo0.92Pt0.08O3 maintained a high NOx removal efficiency after regeneration of a pre-sulfated sample [105]. La0.7Sr0.3 Co0.8Fe0.2O3 perovskite suffers from a drop in NOx removal efficiency after SO2-pretreatment of 6.4% [106]. Wang et al. [107] and Wen et al. [99] compared the sulfur and hydrothermal aging resistance of LaCo0,92Pt0,08O3 and 0.3% Pt/ (Al2O3 + LaCoO3) catalysts, with respect to those shown by 1% Pt–16% Ba/Al2O3 model formulation. These alternatives achieved NOx-to-N2 reduction, sulfur resistance, regeneration, and durability similar or even higher than the model

In summary, perovskite-based formulations achieve notable NO oxidation and NOx adsorption during oxidizing conditions. Furthermore, despite the fact that only a few works analyzed NOx removal during the short reducing period, our results summarized in this chapter remark the potential of perovskite-based materials for application in NOx storage and reduction (NSR) technology for NOx control in diesel and lean-burn engines. In fact, the excellent sulfur tolerance and hydrothermal resistance reported in previous work make these formulations even

As previously observed, stand-alone SCR and NSR systems have some disadvantages that hinder their extended application in both light-duty and heavy-duty vehicles. In the case of the NSR system the high cost, poor thermal stability due to the use of precious metals and nondesired byproduct generation is the main disadvantages, whereas SCR systems require an urea system to provide NH3 and additional device to avoid ammonia slip under transient vehicle operation. The coupling of NSR and SCR catalysts has been rapidly accepted as a potential solution, since its discovery by the Ford Motor company [9, 108]. Different catalytic formulations, system architectures, and operation control have been explored [7, 8, 50, 109, 110]. The systems based on model NSR formulation and Cu/chabazite-type zeolites emerge as the most efficient combination [111]. This hybrid technology has been demonstrated more efficient by maximizing NOx-to-N2 reduction and minimizing NH3 slip with respect to the alone-NSR catalyst. Nevertheless, the most studied NSR formulation used in the combined NSR-SCR system has usually been the conventional Pt-based model catalyst (1.5% Pt-15% BaO/Al2O3), which transfers its high cost and limited hydrothermal stability to the hybrid configuration. Based on the results demonstrated by perovskite-based formulations in the single-NSR technology, their application in combined NSR-SCR systems is considered as

**Figure 6** shows the NOx (NO+NO2), N2O, and NH3 concentration profiles determined by FTIR for the single-NSR and double NSR-SCR configurations at 300°C. The N2 signal determined by mass spectroscopy is also included. NSR and SCR formulations correspond to 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 and 4% Cu/

more promising alternative to Pt-based NSR model catalyst.

an evolution of the current NSR-SCR architecture.

SAPO-34 catalysts, respectively.

**80**

*NOx (NO + NO2) and NH3 outlet concentrations, and MS signal of N2 for the single NSR and NSR-SCR configurations at 300°C. Feed: 500 ppm NO, 6% O2/3% H2, and Ar to balance; W/FA0 = 200 (g h Mol<sup>−</sup><sup>1</sup> ).*

The single-NSR system (**Figure 6a**) shows the typical NOx outlet concentration profile [112]. At the beginning of the lean period, practically all NOx fed are stored, and therefore, concentration of NOx at the reactor outlet is almost null. Then, as the length of the lean period increases, NOx adsorption sites become progressively saturated and NOx outlet concentration increases. In the subsequent rich period, H2 injected releases the stored NOx release and reduces it to a mixture of N2, NH3 and N2O [113]. During this period, the NH3 outlet concentration peaks to almost 1000 ppm (**Figure 6b**). NOx outlet concentration (**Figure 6a**) decreases drastically when the system operates under the NSR-SCR double configuration. As can be observed in **Figure 6b**, most NH3 formed during regeneration of the NSR catalyst is adsorbed on acidic sites of SAPO-34, since concentration of NH3 detected at the outlet of the combined NSR-SCR system is almost zero. Then, in the subsequent lean period, NOx slipping the NSR catalyst reacts with NH3 previously adsorbed on the SCR, leading to further NOx reduction [114].

The evolution of N2 signal also confirms the existence of SCR reaction over the Cu/SAPO-34 catalyst (**Figure 6c**). When the operation is performed with alone-NSR catalyst, formation of N2 was only detected during the rich period, the signal being constant and negligible throughout the storage period. By contrast, when the reaction was carried out with the combined NSR-SCR system, N2 formation was also detected during the storage period. At the beginning of this period, practically all NOx fed are trapped in the NSR catalyst, and therefore, there is no available NOx at the outlet gas stream to carry out the SCR reaction downstream. As a result, the N2 signals at the exit of the NSR catalyst and at the outlet of the NSR-SCR are coincident. As the storage period proceeds, the NSR catalyst becomes saturated, and the gradual increase of NOx concentration at intermediate stream that feeds the SCR catalyst activates its reduction with the NH3 previously stored over the Cu/SAPO-34 catalyst to form the effluent N2 [66].

Thus, the beneficial effect of placing an SCR catalyst downstream of the NSR is demonstrated. Hence, the catalytic behavior of different perovskite-based formulations was compared in a wider range of temperature using a H2 concentration of 3% during the rich period. **Figure 7** quantifies the evolution of NO conversion and N2, NO2, and NH3 productions at 200, 300, and 400°C, for single-NSR and combined NSR-SCR systems. The NSR formulation was varied between 1.5% Pt–15% BaO/ Al2O3 (model catalyst) and 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 (perovskite-based catalyst here formulated).

As a general trend, NO conversion improves with the NSR-SCR configuration irrespective of the NSR catalyst composition used. The implementation of the SCR catalyst in the hybrid configuration also improves production of N2, by consumption of NH3 and NO2 produced in the NSR catalyst. The improvement of NOx removal efficiency up to 300°C is due to higher NH3 production when the SCR catalyst is highly efficiency (200–300°C). In good agreement with this, NH3 production at the outlet decreases significantly for the combined NSR-SCR systems [66]. However, above 300°C, the NH3 production in the NSR catalyst decreases significantly due to the reaction of the NH3 with the stored nitrate downstream (3Ba (NO3)2 + 10NH3 → 3BaO + 8 N2 + 15H2O) of the NSR catalyst [65, 115]. Furthermore, NH3 can be partially oxidized [113, 116], and thus, NH3 generated is insufficient to reduce NOx slipping the upstream NSR system. This explains the

#### **Figure 7.**

*Global conversion of NO (XNO) and product distribution at 200, 300, and 400°C for single-NSR and combined NSR-SCR systems, based on 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 (perovs.) and 1.5% Pt–15% BaO/Al2O3 (model) as NSR catalysts.*

**83**

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust…*

moderate improvement of NOx-to-N2 reduction for the NSR-SCR double configura-

Both configurations show high NO conversion and nitrogen production in the whole temperature range. Specifically, perovskite-based system shows a maximum NO conversion of 99% and a nitrogen production of 92% at 300°C. Indeed, perovskite-based combined NSR-SCR system shows similar or even higher NOxto-N2 reduction efficiencies to that shown by the double configuration when the

In summary, the positive impact of placing an SCR catalyst downstream the NSR catalyst is verified on NOx removal efficiency, with notable increase in N2 production. In this sense, the mixed NSR-SCR system based on the 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 catalyst emerges as a promising alternative, only emitting 7% NH3 at 200°C (slip of NH3), which disappears at higher temperatures achieving NH3 total elimination. This can be considered as a promising starting point for the implementation of these types of oxides in coupled NSR-SCR configurations.

NOx emission removal from lean-burn and diesel engine exhaust gases remains as a technological challenge. To overcome this environmental pollution issue, two main alternatives have been explored during the last decades: NOx storage and reduction (NSR) and selective catalytic reduction with NH3 (NH3-SCR). These alternatives show some limitations that limit their extensive application. In the case of NSR system, some NO can slip without being totally converted, and also, NH3 generated during the rich period can slip as byproduct in the effluent. Furthermore, the catalyst requires high Pt loadings, which limit the cost and thermal stability. On the other hand, NH3-SCR system requires the urea feeding system, which increases the cost and requires an extra volume of the system. Moreover, the latter shows lower NO conversion at low temperatures and allows NH3 slip. As a result, combined NSR-SCR configurations have been explored as an evolution of previous stand-alone technologies. In fact, this hybrid alternative increases the temperature operational window, promotes NO conversion, and avoids the need of urea feeding system. However, up to now, only a conventional Pt-based NSR formulation has

In recent years, efforts have been focused on designing a new generation of NSR catalysts with improved oxidation, adsorption, and reduction capacities. Furthermore, these new materials should be low cost and achieve long hydrothermal stability and high sulfur resistance. Perovskites have gained attention during the recent years as a potential solution. La-based formulations (i.e., LaCoO3 and LaMnO3) have shown excellent NO oxidation conversion, a primary step in the NOx adsorption during lean conditions. In fact, Sr doping further promotes the NO oxidation activity of these formulations, which is closely related to the generation of oxygen vacancies favoring oxygen mobility. However, NOx storage and reduction efficiencies are limited for bulk perovskites due to a low exposed surface area derived from the drastic calcination protocols required during the synthesis process. Supporting perovskite over high surface area materials, e.g., alumina (30% La0.7Sr0.3CoO3/Al2O3), is demonstrated to overcome this limitation. Nonetheless, NOx reduction at low and intermediate temperatures is still limited. The incorporation of low Pd contents over supported perovskite by wetness

impregnation emerges as an efficient solution. In fact, 1.5% Pd–30% La0.7Sr0.3CoO3/ Al2O3 shows similar or even higher NOx removal efficiencies than the conventional NSR model catalyst (1.5% Pt–15% BaO/Al2O3). The activity enhancement showed by perovskite-based formulations motivates their implementation in combined

tion with respect to the single-NSR system at high temperature.

1.5% Pt–15% BaO/Al2O3 model NSR catalyst is used.

been explored in coupled NSR-SCR configurations.

*DOI: http://dx.doi.org/10.5772/intechopen.89532*

**2.4 Outlook and concluding remarks**

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust… DOI: http://dx.doi.org/10.5772/intechopen.89532*

moderate improvement of NOx-to-N2 reduction for the NSR-SCR double configuration with respect to the single-NSR system at high temperature.

Both configurations show high NO conversion and nitrogen production in the whole temperature range. Specifically, perovskite-based system shows a maximum NO conversion of 99% and a nitrogen production of 92% at 300°C. Indeed, perovskite-based combined NSR-SCR system shows similar or even higher NOxto-N2 reduction efficiencies to that shown by the double configuration when the 1.5% Pt–15% BaO/Al2O3 model NSR catalyst is used.

In summary, the positive impact of placing an SCR catalyst downstream the NSR catalyst is verified on NOx removal efficiency, with notable increase in N2 production. In this sense, the mixed NSR-SCR system based on the 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 catalyst emerges as a promising alternative, only emitting 7% NH3 at 200°C (slip of NH3), which disappears at higher temperatures achieving NH3 total elimination. This can be considered as a promising starting point for the implementation of these types of oxides in coupled NSR-SCR configurations.

### **2.4 Outlook and concluding remarks**

*Perovskite Materials, Devices and Integration*

catalyst to form the effluent N2 [66].

catalyst here formulated).

catalyst, formation of N2 was only detected during the rich period, the signal being constant and negligible throughout the storage period. By contrast, when the reaction was carried out with the combined NSR-SCR system, N2 formation was also detected during the storage period. At the beginning of this period, practically all NOx fed are trapped in the NSR catalyst, and therefore, there is no available NOx at the outlet gas stream to carry out the SCR reaction downstream. As a result, the N2 signals at the exit of the NSR catalyst and at the outlet of the NSR-SCR are coincident. As the storage period proceeds, the NSR catalyst becomes saturated, and the gradual increase of NOx concentration at intermediate stream that feeds the SCR catalyst activates its reduction with the NH3 previously stored over the Cu/SAPO-34

Thus, the beneficial effect of placing an SCR catalyst downstream of the NSR is demonstrated. Hence, the catalytic behavior of different perovskite-based formulations was compared in a wider range of temperature using a H2 concentration of 3% during the rich period. **Figure 7** quantifies the evolution of NO conversion and N2, NO2, and NH3 productions at 200, 300, and 400°C, for single-NSR and combined NSR-SCR systems. The NSR formulation was varied between 1.5% Pt–15% BaO/ Al2O3 (model catalyst) and 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 (perovskite-based

As a general trend, NO conversion improves with the NSR-SCR configuration irrespective of the NSR catalyst composition used. The implementation of the SCR catalyst in the hybrid configuration also improves production of N2, by consumption of NH3 and NO2 produced in the NSR catalyst. The improvement of NOx removal efficiency up to 300°C is due to higher NH3 production when the SCR catalyst is highly efficiency (200–300°C). In good agreement with this, NH3 production at the outlet decreases significantly for the combined NSR-SCR systems [66]. However, above 300°C, the NH3 production in the NSR catalyst decreases significantly due to the reaction of the NH3 with the stored nitrate downstream (3Ba

(NO3)2 + 10NH3 → 3BaO + 8 N2 + 15H2O) of the NSR catalyst [65, 115].

Furthermore, NH3 can be partially oxidized [113, 116], and thus, NH3 generated is insufficient to reduce NOx slipping the upstream NSR system. This explains the

*Global conversion of NO (XNO) and product distribution at 200, 300, and 400°C for single-NSR and combined NSR-SCR systems, based on 0.5% Pd–30% La0.5Ba0.5CoO3/Al2O3 (perovs.) and 1.5% Pt–15% BaO/Al2O3*

**82**

**Figure 7.**

*(model) as NSR catalysts.*

NOx emission removal from lean-burn and diesel engine exhaust gases remains as a technological challenge. To overcome this environmental pollution issue, two main alternatives have been explored during the last decades: NOx storage and reduction (NSR) and selective catalytic reduction with NH3 (NH3-SCR). These alternatives show some limitations that limit their extensive application. In the case of NSR system, some NO can slip without being totally converted, and also, NH3 generated during the rich period can slip as byproduct in the effluent. Furthermore, the catalyst requires high Pt loadings, which limit the cost and thermal stability. On the other hand, NH3-SCR system requires the urea feeding system, which increases the cost and requires an extra volume of the system. Moreover, the latter shows lower NO conversion at low temperatures and allows NH3 slip. As a result, combined NSR-SCR configurations have been explored as an evolution of previous stand-alone technologies. In fact, this hybrid alternative increases the temperature operational window, promotes NO conversion, and avoids the need of urea feeding system. However, up to now, only a conventional Pt-based NSR formulation has been explored in coupled NSR-SCR configurations.

In recent years, efforts have been focused on designing a new generation of NSR catalysts with improved oxidation, adsorption, and reduction capacities. Furthermore, these new materials should be low cost and achieve long hydrothermal stability and high sulfur resistance. Perovskites have gained attention during the recent years as a potential solution. La-based formulations (i.e., LaCoO3 and LaMnO3) have shown excellent NO oxidation conversion, a primary step in the NOx adsorption during lean conditions. In fact, Sr doping further promotes the NO oxidation activity of these formulations, which is closely related to the generation of oxygen vacancies favoring oxygen mobility. However, NOx storage and reduction efficiencies are limited for bulk perovskites due to a low exposed surface area derived from the drastic calcination protocols required during the synthesis process. Supporting perovskite over high surface area materials, e.g., alumina (30% La0.7Sr0.3CoO3/Al2O3), is demonstrated to overcome this limitation. Nonetheless, NOx reduction at low and intermediate temperatures is still limited. The incorporation of low Pd contents over supported perovskite by wetness impregnation emerges as an efficient solution. In fact, 1.5% Pd–30% La0.7Sr0.3CoO3/ Al2O3 shows similar or even higher NOx removal efficiencies than the conventional NSR model catalyst (1.5% Pt–15% BaO/Al2O3). The activity enhancement showed by perovskite-based formulations motivates their implementation in combined

NSR-SCR systems, which as an alternative to further improve the NOx removal efficiency of the stand-alone NSR and stand-alone SCR systems. The preliminary results are very promising since NOx**-**to**-**N2 reduction above 90% has been achieved with significant lower noble metal content than platinum in the model catalyst.

Improving the exhaust aftertreatment systems is considered as a critical point in the current vehicle development. In upcoming years, research should be focus on better understanding the mechanism over perovskite-based formulation, especially during regeneration period. Moreover, the NOx trapping efficiency and NOx reduction of the adsorbed NOx can be further promoted. To the best of the authors' knowledge, no studies have been published related to the application of this type of materials to the combined NSR-SCR system. Thus, the room improvement is huge for this application, such as exploring different catalyst architectures (i.e., segmented zones or dual layer monoliths), optimizing precious metal loading, and dispersion. The construction of detailed kinetic model and modeling a full-scale operation will allow to develop a suitable aftertreatment system for automobile application.

## **Acknowledgements**

Support from the Spanish Ministry of Economy and Competiveness (Project CTQ2015-67597-C2-1-R), the Basque Government (IT657-13 and IT1297-19), and the University of the Basque Country acknowledged. One of the authors (JAOC) was supported by a PhD research fellowship provided by the Basque Government (PRE\_2014\_1\_396).

## **Author details**

Jon Ander Onrubia-Calvo, Beñat Pereda-Ayo, Unai De-La-Torre and Juan Ramón González-Velasco\* Chemical Technologies for Environmental Sustainability TQSA, Department of Chemical Engineering, Faculty of Science and Technology, University of the Basque Country UPV/EHU, Leioa, Bizkaia, Spain

\*Address all correspondence to: juanra.gonzalezvelasco@ehu.es

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**85**

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust…*

(15-01-2002)

generation of ammonia for reducing nitrogen oxide. US Patent 6338244 B1

[9] Kinugasa Y, Igarashi K, Itou T, Suzuki N, Yaegashi T, Takeuchi K. Method adsprobed and device for purifying exhaust gas from engine. US

Patent 6047542 (11-04-2000)

for auto exhaust. Science.

science.171.3970.499

science.177.4046.353

DOI: 10.1021/cs500606g

DOI: 10.1021/cr500032a

[14] Gallagher PK, Johnson DW, Schrey F. Studies of some supported perovskite oxidation catalysts. Materials Research Bulletin. 1974;**9**(10):1345-1352. DOI: 10.1016/0025-5408(74)90057-9

[15] Kim CH, Qi G, Dahlberg K, Li W. Strontium-doped perovskites rival platinum catalysts for treating NOx in simulated diesel exhaust. Science. 2010;**327**(5973):1624-1627. DOI:

10.1126/science.1184087

[13] Royer S, Duprez D, Can F, Courtois X, Batiot-Dupeyrat C,

Laassiri S, et al. Perovskites as substitutes of noble metals for heterogeneous catalysis: Dream or reality. Chemical Reviews. 2014;**114**(20):10292-10368.

[10] Libby WF. Promising catalyst

1971;**171**(3970):499. DOI: 10.1126/

[11] Voorhoeve RJH, Remeika JP, Freeland PE, Matthias BT. Rare-earth oxides of manganese and cobalt rival platinum for the treatment of carbon monoxide in auto exhaust. Science. 1972;**177**(4046):353. DOI: 10.1126/

[12] Zhu J, Li H, Zhong L, Xiao P, Xu X, Yang X, et al. Perovskite oxides: Preparation, characterizations, and applications in heterogeneous catalysis. ACS Catalysis. 2014;**4**(9):2917-2940.

*DOI: http://dx.doi.org/10.5772/intechopen.89532*

[1] González-Velasco JR, Pereda-Ayo B,

López-Fonseca R. Coupled NSR-SCR systems for NOx removal in light-duty vehicles. ChemCatChem. 2018;**10**:2928.

[2] Granger P, Parvulescu VI. Catalytic NOx abatement systems for mobile sources: From three-way to lean burn after-treatment technologies. Chemical Reviews. 2011;**111**(5):3155-3207. DOI:

[3] Jabłońska M, Palkovits R. Perovskitebased catalysts for the control of nitrogen oxide emissions from diesel engines. Catalysis Science & Technology. 2019;**9**(9):2057-2077. DOI:

De-La-Torre U, Urrutxua M,

**References**

DOI: 10.1002/cctc.201800392

10.1021/cr100168g

10.1039/C8CY02458H

10.1039/C7CY00983F

[4] Granger P. Challenges and breakthrough in post-combustion catalysis: How to match future stringent

regulations? Catalysis Science & Technology. 2017;**7**:5195-5211. DOI:

[5] De-La-Torre U, Pereda-Ayo B,

10.1007/s11244-018-1016-0

[6] Gandhi HS, Cavatalo JV,

[7] Gandhi HS, Cavatalo JV,

and apparatus with internal

7332135 (19-02-2008)

Onrubia JA, González-Velasco JR. Effect of the presence of ceria in the NSR catalyst on the hydrothermal resistance and global DeNOx performance of coupled LNT-SCR systems. Topics in Catalysis. 2018;**61**(18):1993-2006. DOI:

Hammerle RH, Chen Y. Catalyst system for NOx and NH3 emission. US Patent

Hammerle RH, Chen Y. Catalyst system for NOx and NH3 emission. US Patent Appl. 2004/0076565 A1 (22-04-2004)

[8] Guenther J, Konrad B, Krutzsch B, Nolte A, Voigtlaender D, Weibel M, et al. Exhaust gas purification process *Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust… DOI: http://dx.doi.org/10.5772/intechopen.89532*

## **References**

*Perovskite Materials, Devices and Integration*

application.

**Acknowledgements**

(PRE\_2014\_1\_396).

**Author details**

and Juan Ramón González-Velasco\*

Country UPV/EHU, Leioa, Bizkaia, Spain

provided the original work is properly cited.

NSR-SCR systems, which as an alternative to further improve the NOx removal efficiency of the stand-alone NSR and stand-alone SCR systems. The preliminary results are very promising since NOx**-**to**-**N2 reduction above 90% has been achieved with significant lower noble metal content than platinum in the model catalyst. Improving the exhaust aftertreatment systems is considered as a critical point in the current vehicle development. In upcoming years, research should be focus on better understanding the mechanism over perovskite-based formulation, especially during regeneration period. Moreover, the NOx trapping efficiency and NOx reduction of the adsorbed NOx can be further promoted. To the best of the authors' knowledge, no studies have been published related to the application of this type of materials to the combined NSR-SCR system. Thus, the room improvement is huge for this application, such as exploring different catalyst architectures (i.e., segmented zones or dual layer monoliths), optimizing precious metal loading, and dispersion. The construction of detailed kinetic model and modeling a full-scale operation will allow to develop a suitable aftertreatment system for automobile

Support from the Spanish Ministry of Economy and Competiveness (Project CTQ2015-67597-C2-1-R), the Basque Government (IT657-13 and IT1297-19), and the University of the Basque Country acknowledged. One of the authors (JAOC) was supported by a PhD research fellowship provided by the Basque Government

Jon Ander Onrubia-Calvo, Beñat Pereda-Ayo, Unai De-La-Torre

\*Address all correspondence to: juanra.gonzalezvelasco@ehu.es

Chemical Technologies for Environmental Sustainability TQSA, Department of Chemical Engineering, Faculty of Science and Technology, University of the Basque

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

**84**

[1] González-Velasco JR, Pereda-Ayo B, De-La-Torre U, Urrutxua M, López-Fonseca R. Coupled NSR-SCR systems for NOx removal in light-duty vehicles. ChemCatChem. 2018;**10**:2928. DOI: 10.1002/cctc.201800392

[2] Granger P, Parvulescu VI. Catalytic NOx abatement systems for mobile sources: From three-way to lean burn after-treatment technologies. Chemical Reviews. 2011;**111**(5):3155-3207. DOI: 10.1021/cr100168g

[3] Jabłońska M, Palkovits R. Perovskitebased catalysts for the control of nitrogen oxide emissions from diesel engines. Catalysis Science & Technology. 2019;**9**(9):2057-2077. DOI: 10.1039/C8CY02458H

[4] Granger P. Challenges and breakthrough in post-combustion catalysis: How to match future stringent regulations? Catalysis Science & Technology. 2017;**7**:5195-5211. DOI: 10.1039/C7CY00983F

[5] De-La-Torre U, Pereda-Ayo B, Onrubia JA, González-Velasco JR. Effect of the presence of ceria in the NSR catalyst on the hydrothermal resistance and global DeNOx performance of coupled LNT-SCR systems. Topics in Catalysis. 2018;**61**(18):1993-2006. DOI: 10.1007/s11244-018-1016-0

[6] Gandhi HS, Cavatalo JV, Hammerle RH, Chen Y. Catalyst system for NOx and NH3 emission. US Patent 7332135 (19-02-2008)

[7] Gandhi HS, Cavatalo JV, Hammerle RH, Chen Y. Catalyst system for NOx and NH3 emission. US Patent Appl. 2004/0076565 A1 (22-04-2004)

[8] Guenther J, Konrad B, Krutzsch B, Nolte A, Voigtlaender D, Weibel M, et al. Exhaust gas purification process and apparatus with internal

generation of ammonia for reducing nitrogen oxide. US Patent 6338244 B1 (15-01-2002)

[9] Kinugasa Y, Igarashi K, Itou T, Suzuki N, Yaegashi T, Takeuchi K. Method adsprobed and device for purifying exhaust gas from engine. US Patent 6047542 (11-04-2000)

[10] Libby WF. Promising catalyst for auto exhaust. Science. 1971;**171**(3970):499. DOI: 10.1126/ science.171.3970.499

[11] Voorhoeve RJH, Remeika JP, Freeland PE, Matthias BT. Rare-earth oxides of manganese and cobalt rival platinum for the treatment of carbon monoxide in auto exhaust. Science. 1972;**177**(4046):353. DOI: 10.1126/ science.177.4046.353

[12] Zhu J, Li H, Zhong L, Xiao P, Xu X, Yang X, et al. Perovskite oxides: Preparation, characterizations, and applications in heterogeneous catalysis. ACS Catalysis. 2014;**4**(9):2917-2940. DOI: 10.1021/cs500606g

[13] Royer S, Duprez D, Can F, Courtois X, Batiot-Dupeyrat C, Laassiri S, et al. Perovskites as substitutes of noble metals for heterogeneous catalysis: Dream or reality. Chemical Reviews. 2014;**114**(20):10292-10368. DOI: 10.1021/cr500032a

[14] Gallagher PK, Johnson DW, Schrey F. Studies of some supported perovskite oxidation catalysts. Materials Research Bulletin. 1974;**9**(10):1345-1352. DOI: 10.1016/0025-5408(74)90057-9

[15] Kim CH, Qi G, Dahlberg K, Li W. Strontium-doped perovskites rival platinum catalysts for treating NOx in simulated diesel exhaust. Science. 2010;**327**(5973):1624-1627. DOI: 10.1126/science.1184087

[16] Onrubia JA, Pereda-Ayo B, De-La-Torre U, González-Velasco JR. Key factors in Sr-doped LaBO3 (B=Co or Mn) perovskites for NO oxidation in efficient diesel exhaust purification. Applied Catalysis B: Environmental. 2017;**213**:198-210. DOI: 10.1016/j. apcatb.2017.04.068

[17] Zhou C, Feng Z, Zhang Y, Hu L, Chen R, Shan B, et al. Enhanced catalytic activity for NO oxidation over Ba doped LaCoO3 catalyst. RSC Advances. 2015;**5**(36):28054-28059. DOI: 10.1039/C5RA02344K

[18] Wen Y, Zhang C, He H, Yu Y, Teraoka Y. Catalytic oxidation of nitrogen monoxide over La1−xCexCoO3 perovskites. Catalysis Today. 2007;**126**(3):400-405. DOI: 10.1016/j. cattod.2007.06.032

[19] Wang J, Su Y, Wang X, Chen J, Zhao Z, Shen M. The effect of partial substitution of Co in LaMnO3 synthesized by sol–gel methods for NO oxidation. Catalysis Communications. 2012;**25**:106-109. DOI: 10.1016/j. catcom.2012.04.001

[20] Zhou C, Liu X, Wu C, Wen Y, Xue Y, Chen R, et al. NO oxidation catalysis on copper doped hexagonal phase LaCoO3: A combined experimental and theoretical study. Physical Chemistry Chemical Physics. 2014;**16**(11): 5106-5112. DOI: 10.1039/C3CP54963A

[21] Zhong S, Sun Y, Xin H, Yang C, Chen L, Li X. NO oxidation over Ni-Co perovskite catalysts. Chemical Engineering Journal. 2015;**275**:351-356. DOI: 10.1016/j.cej.2015.04.046

[22] Hong Z, Wang Z, Li X. Catalytic oxidation of nitric oxide (NO) over different catalysts: An overview. Catalysis Science & Technology. 2017;**7**(16): 3440-3452. DOI: 10.1039/C7CY00760D

[23] Zhu J, Thomas A. ChemInform abstract: Perovskite-type mixed oxides as catalytic material for NO removal. Applied Catalysis B: Environmental. 2010;**41**:225-233. DOI: 10.1016/j. apcatb.2009.08.008

[24] Hong S, Lee G. Simultaneous removal of NO and carbon particulates over lanthanoid perovskitetype catalysts. Catalysis Today. 2000;**63**(2):397-404. DOI: 10.1016/ S0920-5861(00)00484-3

[25] Liu J, Xu J, Zhao Z, Duan A, Jiang G, Jing Y. A novel four-way combining catalysts for simultaneous removal of exhaust pollutants from diesel engine. Journal of Environmental Sciences. 2010;**22**(7):1104-1109. DOI: 10.1016/ S1001-0742(09)60224-2

[26] Li Z, Meng M, Li Q, Xie Y, Hu T, Zhang J. Fe-substituted nanometric La0.9K0.1Co1−xFexO3−δ perovskite catalysts used for soot combustion, NOx storage and simultaneous catalytic removal of soot and NOx. Chemical Engineering Journal. 2010;**164**(1):98- 105. DOI: 10.1016/j.cej.2010.08.036

[27] Mescia D, Caroca JC, Russo N, Labhsetwar N, Fino D, Saracco G, et al. Towards a single brick solution for the abatement of NOx and soot from diesel engine exhausts. Catalysis Today. 2008;**137**(2):300-305. DOI: 10.1016/j. cattod.2007.11.010

[28] Teraoka Y, Kanada K, Kagawa S. Synthesis of La1-xKxMnO perovskite-type oxides and their catalytic property for simultaneous removal of NOx and diesel soot particulates. Applied Catalysis B: Environmental. 2001;**34**(1):73-78. DOI: 10.1016/S0926-3373(01)00202-8

[29] Yao W, Wang R, Yang X. LaCo1-x PdxO3 perovskite-type oxides: Synthesis, characterization and simultaneous removal of NOx and diesel soot. Catalysis Letters. 2009;**130**(3): 613-621. DOI: 10.1007/s10562- 009-9905-2

**87**

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust…*

BF00807194

[36] Gunasekaran N, Rajadurai S, Carberry JJ. Catalytic decomposition of nitrous oxide over perovskite type solid oxide solutions and supported noble metal catalysts. Catalysis Letters. 1995;**35**(3):373-382. DOI: 10.1007/

[37] Pan KL, Yu SJ, Yan SY, Chang MB. Direct N2O decomposition over La2NiO4-based perovskite-type oxides. Journal of the Air & Waste Management Association. 2014;**64**(11):1260-1269. DOI: 10.1080/10962247.2014.941513

[38] Alini S, Basile F, Blasioli S, Rinaldi C, Vaccari A. Development of new catalysts for N2O-decomposition from adipic acid plant. Applied Catalysis B: Environmental. 2007;**70**(1):323-329. DOI: 10.1016/j.apcatb.2005.12.031

[39] Belessi VC, Trikalitis PN, Ladavos AK, Bakas TV, Pomonis PJ. Structure and catalytic activity of La1−xFeO3 system (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.35) for the NO+CO reaction. Applied Catalysis A: General. 1999;**177**. DOI: 10.1016/S0926-860X

[40] Belessi VC, Bakas TV, Costa CN, Efstathiou AM, Pomonis PJ. Synergistic effects of crystal phases and mixed valences in La–Sr–Ce–Fe–O mixed oxidic/perovskitic solids on their catalytic activity for the NO+CO reaction. Applied Catalysis B:

Environmental. 2000;**28**(1):13-28. DOI: 10.1016/S0926-3373(00)00159-4

[41] Leontiou AA, Ladavos AK, Pomonis PJ. Catalytic NO reduction with CO on La1−xSrx(Fe3+/Fe4+)O3±<sup>δ</sup> perovskite-type mixed oxides (x = 0.00, 0.15, 0.30, 0.40, 0.60, 0.70, 0.80, and 0.90). Applied Catalysis A: General. 2003;**241**(1):133-141. DOI: 10.1016/

S0926-860X(02)00457-X

[42] Wang Y, Cui X, Li Y, Shu Z,

Chen H, Shi J. A simple co-nanocasting method to synthesize high surface area

(98)00256-7

*DOI: http://dx.doi.org/10.5772/intechopen.89532*

[30] Wang K, Qian L, Zhang L, Liu H, Yan Z. Simultaneous removal

[31] Dhal GC, Dey S, Mohan D, Prasad R. Study of Fe, Co, and Mn-based perovskite-type catalysts for the simultaneous control of soot and NOX from diesel engine exhaust. Materials Discovery. 2017;**10**:37-42. DOI: 10.1016/j.md.2018.04.002

[32] Sun K, Xia H, Hensen E, van Santen R, Li C. Chemistry of N2O decomposition on active sites with different nature: Effect of hightemperature treatment of Fe/ZSM-5. Journal of Catalysis. 2006;**238**(1): 186-195. DOI: 10.1016/j.jcat.2005.12.013

[33] Ivanov DV, Sadovskaya EM, Pinaeva LG, Isupova LA. Influence of oxygen mobility on catalytic activity of La–Sr–Mn–O composites in the reaction of high temperature N2O decomposition. Journal of Catalysis. 2009;**267**(1):5-13. DOI: 10.1016/j.

[34] Ivanov DV, Pinaeva LG, Isupova LA, Sadovskaya EM, Prosvirin IP, Gerasimov EY, et al. Effect of surface decoration with LaSrFeO4 on oxygen mobility and catalytic activity of La0.4Sr0.6FeO3−δ in high-temperature N2O decomposition, methane combustion and ammonia oxidation. Applied Catalysis A: General.

2013;**457**:42-51. DOI: 10.1016/j.

[35] Wu Y, Dujardin C, Lancelot C, Dacquin JP, Parvulescu VI, Cabié M, et al. Catalytic abatement of NO and N2O from nitric acid plants: A novel approach using noble metal-modified perovskites. Journal of Catalysis. 2015;**328**:236-247. DOI: 10.1016/j.

apcata.2013.03.007

jcat.2015.02.001

jcat.2009.07.005

of NOx and soot particulates over La0.7Ag0.3MnO3 perovskite oxide catalysts. Catalysis Today. 2010;**158**(3):423-426. DOI: 10.1016/j.

cattod.2010.06.001

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust… DOI: http://dx.doi.org/10.5772/intechopen.89532*

[30] Wang K, Qian L, Zhang L, Liu H, Yan Z. Simultaneous removal of NOx and soot particulates over La0.7Ag0.3MnO3 perovskite oxide catalysts. Catalysis Today. 2010;**158**(3):423-426. DOI: 10.1016/j. cattod.2010.06.001

*Perovskite Materials, Devices and Integration*

De-La-Torre U, González-Velasco JR. Key factors in Sr-doped LaBO3 (B=Co or Mn) perovskites for NO oxidation in efficient diesel exhaust purification. Applied Catalysis B: Environmental. 2017;**213**:198-210. DOI: 10.1016/j.

as catalytic material for NO removal. Applied Catalysis B: Environmental. 2010;**41**:225-233. DOI: 10.1016/j.

[24] Hong S, Lee G. Simultaneous removal of NO and carbon particulates

[25] Liu J, Xu J, Zhao Z, Duan A, Jiang G, Jing Y. A novel four-way combining catalysts for simultaneous removal of exhaust pollutants from diesel engine. Journal of Environmental Sciences. 2010;**22**(7):1104-1109. DOI: 10.1016/

[26] Li Z, Meng M, Li Q, Xie Y, Hu T, Zhang J. Fe-substituted nanometric La0.9K0.1Co1−xFexO3−δ perovskite catalysts used for soot combustion, NOx storage and simultaneous catalytic removal of soot and NOx. Chemical Engineering Journal. 2010;**164**(1):98- 105. DOI: 10.1016/j.cej.2010.08.036

[27] Mescia D, Caroca JC, Russo N, Labhsetwar N, Fino D, Saracco G, et al. Towards a single brick solution for the abatement of NOx and soot from diesel engine exhausts. Catalysis Today. 2008;**137**(2):300-305. DOI: 10.1016/j.

Kagawa S. Synthesis of La1-xKxMnO perovskite-type oxides and their catalytic property for simultaneous removal of NOx and diesel soot particulates. Applied Catalysis B: Environmental. 2001;**34**(1):73-78. DOI: 10.1016/S0926-3373(01)00202-8

[29] Yao W, Wang R, Yang X. LaCo1-x PdxO3 perovskite-type oxides: Synthesis, characterization and simultaneous removal of NOx and diesel soot. Catalysis Letters. 2009;**130**(3): 613-621. DOI: 10.1007/s10562-

cattod.2007.11.010

009-9905-2

[28] Teraoka Y, Kanada K,

over lanthanoid perovskitetype catalysts. Catalysis Today. 2000;**63**(2):397-404. DOI: 10.1016/

S0920-5861(00)00484-3

S1001-0742(09)60224-2

apcatb.2009.08.008

[16] Onrubia JA, Pereda-Ayo B,

[17] Zhou C, Feng Z, Zhang Y,

DOI: 10.1039/C5RA02344K

perovskites. Catalysis Today.

substitution of Co in LaMnO3

cattod.2007.06.032

catcom.2012.04.001

[18] Wen Y, Zhang C, He H, Yu Y, Teraoka Y. Catalytic oxidation of nitrogen monoxide over La1−xCexCoO3

2007;**126**(3):400-405. DOI: 10.1016/j.

[19] Wang J, Su Y, Wang X, Chen J, Zhao Z, Shen M. The effect of partial

synthesized by sol–gel methods for NO oxidation. Catalysis Communications. 2012;**25**:106-109. DOI: 10.1016/j.

[20] Zhou C, Liu X, Wu C, Wen Y, Xue Y, Chen R, et al. NO oxidation catalysis on copper doped hexagonal phase LaCoO3: A combined experimental and theoretical study. Physical Chemistry Chemical Physics. 2014;**16**(11): 5106-5112. DOI: 10.1039/C3CP54963A

[21] Zhong S, Sun Y, Xin H, Yang C, Chen L, Li X. NO oxidation over Ni-Co

Engineering Journal. 2015;**275**:351-356.

[22] Hong Z, Wang Z, Li X. Catalytic oxidation of nitric oxide (NO) over different catalysts: An overview. Catalysis Science & Technology. 2017;**7**(16): 3440-3452. DOI: 10.1039/C7CY00760D

[23] Zhu J, Thomas A. ChemInform abstract: Perovskite-type mixed oxides

perovskite catalysts. Chemical

DOI: 10.1016/j.cej.2015.04.046

Hu L, Chen R, Shan B, et al. Enhanced catalytic activity for NO oxidation over Ba doped LaCoO3 catalyst. RSC Advances. 2015;**5**(36):28054-28059.

apcatb.2017.04.068

**86**

[31] Dhal GC, Dey S, Mohan D, Prasad R. Study of Fe, Co, and Mn-based perovskite-type catalysts for the simultaneous control of soot and NOX from diesel engine exhaust. Materials Discovery. 2017;**10**:37-42. DOI: 10.1016/j.md.2018.04.002

[32] Sun K, Xia H, Hensen E, van Santen R, Li C. Chemistry of N2O decomposition on active sites with different nature: Effect of hightemperature treatment of Fe/ZSM-5. Journal of Catalysis. 2006;**238**(1): 186-195. DOI: 10.1016/j.jcat.2005.12.013

[33] Ivanov DV, Sadovskaya EM, Pinaeva LG, Isupova LA. Influence of oxygen mobility on catalytic activity of La–Sr–Mn–O composites in the reaction of high temperature N2O decomposition. Journal of Catalysis. 2009;**267**(1):5-13. DOI: 10.1016/j. jcat.2009.07.005

[34] Ivanov DV, Pinaeva LG, Isupova LA, Sadovskaya EM, Prosvirin IP, Gerasimov EY, et al. Effect of surface decoration with LaSrFeO4 on oxygen mobility and catalytic activity of La0.4Sr0.6FeO3−δ in high-temperature N2O decomposition, methane combustion and ammonia oxidation. Applied Catalysis A: General. 2013;**457**:42-51. DOI: 10.1016/j. apcata.2013.03.007

[35] Wu Y, Dujardin C, Lancelot C, Dacquin JP, Parvulescu VI, Cabié M, et al. Catalytic abatement of NO and N2O from nitric acid plants: A novel approach using noble metal-modified perovskites. Journal of Catalysis. 2015;**328**:236-247. DOI: 10.1016/j. jcat.2015.02.001

[36] Gunasekaran N, Rajadurai S, Carberry JJ. Catalytic decomposition of nitrous oxide over perovskite type solid oxide solutions and supported noble metal catalysts. Catalysis Letters. 1995;**35**(3):373-382. DOI: 10.1007/ BF00807194

[37] Pan KL, Yu SJ, Yan SY, Chang MB. Direct N2O decomposition over La2NiO4-based perovskite-type oxides. Journal of the Air & Waste Management Association. 2014;**64**(11):1260-1269. DOI: 10.1080/10962247.2014.941513

[38] Alini S, Basile F, Blasioli S, Rinaldi C, Vaccari A. Development of new catalysts for N2O-decomposition from adipic acid plant. Applied Catalysis B: Environmental. 2007;**70**(1):323-329. DOI: 10.1016/j.apcatb.2005.12.031

[39] Belessi VC, Trikalitis PN, Ladavos AK, Bakas TV, Pomonis PJ. Structure and catalytic activity of La1−xFeO3 system (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.35) for the NO+CO reaction. Applied Catalysis A: General. 1999;**177**. DOI: 10.1016/S0926-860X (98)00256-7

[40] Belessi VC, Bakas TV, Costa CN, Efstathiou AM, Pomonis PJ. Synergistic effects of crystal phases and mixed valences in La–Sr–Ce–Fe–O mixed oxidic/perovskitic solids on their catalytic activity for the NO+CO reaction. Applied Catalysis B: Environmental. 2000;**28**(1):13-28. DOI: 10.1016/S0926-3373(00)00159-4

[41] Leontiou AA, Ladavos AK, Pomonis PJ. Catalytic NO reduction with CO on La1−xSrx(Fe3+/Fe4+)O3±<sup>δ</sup> perovskite-type mixed oxides (x = 0.00, 0.15, 0.30, 0.40, 0.60, 0.70, 0.80, and 0.90). Applied Catalysis A: General. 2003;**241**(1):133-141. DOI: 10.1016/ S0926-860X(02)00457-X

[42] Wang Y, Cui X, Li Y, Shu Z, Chen H, Shi J. A simple co-nanocasting method to synthesize high surface area

mesoporous LaCoO3 oxides for CO and NO oxidations. Microporous and Mesoporous Materials. 2013;**176**:8-15. DOI: 10.1016/j.micromeso.2013.03.033

[43] Peter SD, Garbowski E, Perrichon V, Primet M. NO reduction by CO over aluminate-supported perovskites. Catalysis Letters. 2000;**70**(1):27-33. DOI: 10.1023/A:1019027619209

[44] Shen S, Weng H. Comparative study of catalytic reduction of nitric oxide with carbon monoxide over the La1 xSrxBO3 (B = Mn, Fe, Co, Ni) catalysts. Industrial and Engineering Chemistry Research. 1998;**37**(7):2654-2661. DOI: 10.1021/ie970691g

[45] Varma S, Wani BN, Gupta NM. Redox behavior and catalytic activity of La–Fe–V–O mixed oxides. Applied Catalysis A: General. 2003;**241**(1):341-348. DOI: 10.1016/ S0926-860X(02)00492-1

[46] De-La-Torre U, Pereda-Ayo B, Gutiérrez-Ortiz MA, González-Marcos JA, González-Velasco JR. Steady-state NH3- SCR global model and kinetic parameter estimation for NOx removal in diesel engine exhaust aftertreatment with Cu/ chabazite. Catalysis Today. 2017;**296**:95- 104. DOI: 10.1016/j.cattod.2017.04.011

[47] Cavataio G, Girard J, Eli Patterson J, Montreuil C, Cheng Y, Lambert C. Laboratory testing of urea-SCR formulations to meet tier 2 bin 5 emissions, SAE Technical Paper 2007-01-1575. 2007. DOI: 10.4271/ 2007-01-1575

[48] Koebel M, Elsener M, Marti T. NOxreduction in diesel exhaust gas with urea and selective catalytic reduction. Combustion Science and Technology. 1996;**121**(1-6):85-102. DOI: 10.1080/00102209608935588

[49] Nova I, Tronconi E, editors. Urea-SCR Technology for DeNOx After Treatment of Diesel Exhausts. Berlin: Springer; 2014. 715p. DOI: 10.1080/00102209608935588

[50] Urrutxua M, Pereda-Ayo B, Trandafilovic LV, Olsson L, González-Velasco JR. Influence of H2, CO, C3H6, and C7H8 as reductants on DeNOx behavior of dual monoliths for NOx storage/reduction coupled with selective catalytic reduction. Industrial and Engineering Chemistry Research. 2019;**58**(17):7001-7013. DOI: 10.1021/ acs.iecr.9b00149

[51] De La Torre U, Pereda-Ayo B, González-Velasco JR. Cu-zeolite NH3- SCR catalysts for NOx removal in the combined NSR–SCR technology. Chemical Engineering Journal. 2012;**207-208**:10-17. DOI: 10.1016/j. cej.2012.06.092

[52] Zhu Z, Liu Z, Niu H, Liu S. Promoting effect of SO2 on activated carbon-supported vanadia catalyst for NO reduction by NH3 at low temperatures. Journal of Catalysis. 1999;**187**(1):245-248. DOI: 10.1006/ jcat.1999.2605

[53] Tang X, Hao J, Xu W, Li J. Low temperature selective catalytic reduction of NOx with NH3 over amorphous MnOx catalysts prepared by three methods. Catalysis Communications. 2007;**8**(3):329-334. DOI: 10.1016/j.catcom.2006.06.025

[54] Singoredjo L, Korver R, Kapteijn F, Moulijn J. Alumina supported manganese oxides for the low-temperature selective catalytic reduction of nitric oxide with ammonia. Applied Catalysis B: Environmental. 1992;**1**(4):297-316. DOI: 10.1016/0926-3373(92)80055-5

[55] Chmielarz L, Jabłońska M, Strumiński A, Piwowarska Z, Węgrzyn A, Witkowski S, et al. Selective catalytic oxidation of ammonia to nitrogen over Mg-Al, Cu-Mg-Al and Fe-Mg-Al mixed metal oxides doped with noble metals.

**89**

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust…*

[62] Nova I, Castoldi L, Lietti L,

[63] Nova I, Castoldi L, Lietti L, Tronconi E, Forzatti P, Prinetto F, Ghiotti G. NOx adsorption study over Pt–Ba/alumina catalysts: FT-IR and pulse experiments. Journal of Catalysis. 2004;**222**(2):377-388. DOI: 10.1016/j.

[64] Lietti L, Forzatti P, Nova I, Tronconi E. NOx storage reduction over Pt-Ba/γ-Al2O3 catalyst. Journal of Catalysis. 2001;**204**(1):175-191. DOI:

[65] Lietti L, Nova I, Forzatti P. Role of ammonia in the reduction by hydrogen of NOx stored over Pt–Ba/Al2O3 lean NOx trap catalysts. Journal of Catalysis. 2008;**257**(2):270-282. DOI: 10.1016/j.

[66] Onrubia-Calvo JA. Perovskites as alternative for NOx storage and reduction systems: formulations, mechanism and optimal control [thesis]. Leioa: Universidad del País

[67] You R, Meng M, Zhang J, Zheng L, Hu T, Li X. A noble-metal-free SCR-LNT coupled catalytic system used for high-concentration NOx reduction under lean-burn condition. Catalysis Today. 2019;**327**:347-356. DOI: 10.1016/j.

10.1006/jcat.2001.3370

jcat.2008.05.005

Vasco; 2019

cattod.2018.03.022

10.1081/CR-200031932

González-Marcos MP,

[68] Epling WS, Campbell LE, Yezerets A, Currier NW, Parks JE. Overview of the fundamental reactions and degradation mechanisms of NOx storage/reduction catalysts. Catalysis Reviews. 2004;**46**(2):163-245. DOI:

[69] Pereda-Ayo B, De La Torre U,

S0920-5861(02)00093-7

jcat.2003.11.013

Tronconi E, Forzatti P. On the dynamic behavior of NOx storage/reduction Pt–Ba/Al2O3 catalyst. Catalysis Today. 2002;**75**(1):431-437. DOI: 10.1016/

*DOI: http://dx.doi.org/10.5772/intechopen.89532*

Applied Catalysis B: Environmental. 2013;**130-131**:152-162. DOI: 10.1016/j.

[56] Zhang R, Luo N, Yang W, Liu N, Chen B. Low-temperature selective catalytic reduction of NO with NH3 using perovskite-type oxides as the novel catalysts. Journal of Molecular Catalysis A: Chemical. 2013;**371**:86-93. DOI: 10.1016/j.molcata.2013.01.018

[57] Zhang R, Yang W, Luo N, Li P, Lei Z, Chen B. Low-temperature NH3- SCR of NO by lanthanum manganite perovskites: Effect of A-/B-site substitution and TiO2/CeO2 support. Applied Catalysis B: Environmental. 2014;**146**:94-104. DOI: 10.1016/j.

[58] Zhang Y, Wang D, Wang J, Chen Q, Zhang Z, Pan X, et al. BiMnO3 perovskite catalyst for selective catalytic reduction of NO with NH3 at low temperature. Chinese Journal of Catalysis. 2012;**33**(9):1448-1454. DOI: 10.1016/S1872-2067(11)60439-7

[59] Shi H, Li X, Xia J, Lu X, Zuo S, Luo S, et al. Sol-gel synthesis of LaBO3/

attapulgite (B=Mn, Fe, Co, Ni) nanocomposite for NH3-SCR of NO at low temperature. Journal of Inorganic

and Organometallic Polymers. 2017;**27**(1):166-172. DOI: 10.1007/

[60] Wallin M, Cruise N, Klement U, Palmqvist A, Skoglundh M. Preparation of Mn, Fe and Co based perovskite catalysts using microemulsions. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2004;**238**(1):27-35. DOI: 10.1016/j.colsurfa.2004.02.019

[61] Takahashi N, Shinjoh H, Iijima T, Suzuki T, Yamazaki K, Yokota K, et al. The new concept 3-way catalyst for automotive lean-burn engine: NOx storage and reduction catalyst. Catalysis Today. 1996;**27**(1):63-69. DOI:

10.1016/0920-5861(95)00173-5

s10904-017-0683-9

apcatb.2012.11.004

apcatb.2013.04.047

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust… DOI: http://dx.doi.org/10.5772/intechopen.89532*

Applied Catalysis B: Environmental. 2013;**130-131**:152-162. DOI: 10.1016/j. apcatb.2012.11.004

*Perovskite Materials, Devices and Integration*

mesoporous LaCoO3 oxides for CO and NO oxidations. Microporous and Mesoporous Materials. 2013;**176**:8-15. DOI: 10.1016/j.micromeso.2013.03.033

[43] Peter SD, Garbowski E, Perrichon V, Primet M. NO reduction by CO over aluminate-supported perovskites. Catalysis Letters. 2000;**70**(1):27-33. DOI: 10.1023/A:1019027619209

Berlin: Springer; 2014. 715p. DOI: 10.1080/00102209608935588

[50] Urrutxua M, Pereda-Ayo B, Trandafilovic LV, Olsson L,

[51] De La Torre U, Pereda-Ayo B, González-Velasco JR. Cu-zeolite NH3- SCR catalysts for NOx removal in the combined NSR–SCR technology. Chemical Engineering Journal. 2012;**207-208**:10-17. DOI: 10.1016/j.

[52] Zhu Z, Liu Z, Niu H, Liu S. Promoting effect of SO2 on activated carbon-supported vanadia catalyst for NO reduction by NH3 at low temperatures. Journal of Catalysis. 1999;**187**(1):245-248. DOI: 10.1006/

[53] Tang X, Hao J, Xu W, Li J. Low temperature selective catalytic reduction of NOx with NH3 over amorphous MnOx catalysts prepared

Communications. 2007;**8**(3):329-334. DOI: 10.1016/j.catcom.2006.06.025

by three methods. Catalysis

[54] Singoredjo L, Korver R, Kapteijn F, Moulijn J. Alumina supported manganese oxides for the low-temperature selective catalytic reduction of nitric oxide with ammonia. Applied Catalysis B: Environmental. 1992;**1**(4):297-316. DOI:

10.1016/0926-3373(92)80055-5

[55] Chmielarz L, Jabłońska M,

Strumiński A, Piwowarska Z, Węgrzyn A, Witkowski S, et al. Selective catalytic oxidation of ammonia to nitrogen over Mg-Al, Cu-Mg-Al and Fe-Mg-Al mixed metal oxides doped with noble metals.

acs.iecr.9b00149

cej.2012.06.092

jcat.1999.2605

González-Velasco JR. Influence of H2, CO, C3H6, and C7H8 as reductants on DeNOx behavior of dual monoliths for NOx storage/reduction coupled with selective catalytic reduction. Industrial and Engineering Chemistry Research. 2019;**58**(17):7001-7013. DOI: 10.1021/

[44] Shen S, Weng H. Comparative study of catalytic reduction of nitric oxide with carbon monoxide over the La1 xSrxBO3 (B = Mn, Fe, Co, Ni) catalysts. Industrial and Engineering Chemistry Research. 1998;**37**(7):2654-2661. DOI:

[45] Varma S, Wani BN, Gupta NM. Redox behavior and catalytic activity

[46] De-La-Torre U, Pereda-Ayo B, Gutiérrez-Ortiz MA, González-Marcos JA, González-Velasco JR. Steady-state NH3- SCR global model and kinetic parameter estimation for NOx removal in diesel engine exhaust aftertreatment with Cu/ chabazite. Catalysis Today. 2017;**296**:95- 104. DOI: 10.1016/j.cattod.2017.04.011

of La–Fe–V–O mixed oxides. Applied Catalysis A: General. 2003;**241**(1):341-348. DOI: 10.1016/

S0926-860X(02)00492-1

[47] Cavataio G, Girard J, Eli Patterson J, Montreuil C, Cheng Y, Lambert C. Laboratory testing of urea-SCR formulations to meet tier 2 bin 5 emissions, SAE Technical Paper 2007-01-1575. 2007. DOI: 10.4271/

[48] Koebel M, Elsener M, Marti T. NOx-

reduction in diesel exhaust gas with urea and selective catalytic reduction. Combustion Science and Technology. 1996;**121**(1-6):85-102. DOI:

10.1080/00102209608935588

[49] Nova I, Tronconi E, editors. Urea-SCR Technology for DeNOx After Treatment of Diesel Exhausts.

2007-01-1575

10.1021/ie970691g

**88**

[56] Zhang R, Luo N, Yang W, Liu N, Chen B. Low-temperature selective catalytic reduction of NO with NH3 using perovskite-type oxides as the novel catalysts. Journal of Molecular Catalysis A: Chemical. 2013;**371**:86-93. DOI: 10.1016/j.molcata.2013.01.018

[57] Zhang R, Yang W, Luo N, Li P, Lei Z, Chen B. Low-temperature NH3- SCR of NO by lanthanum manganite perovskites: Effect of A-/B-site substitution and TiO2/CeO2 support. Applied Catalysis B: Environmental. 2014;**146**:94-104. DOI: 10.1016/j. apcatb.2013.04.047

[58] Zhang Y, Wang D, Wang J, Chen Q, Zhang Z, Pan X, et al. BiMnO3 perovskite catalyst for selective catalytic reduction of NO with NH3 at low temperature. Chinese Journal of Catalysis. 2012;**33**(9):1448-1454. DOI: 10.1016/S1872-2067(11)60439-7

[59] Shi H, Li X, Xia J, Lu X, Zuo S, Luo S, et al. Sol-gel synthesis of LaBO3/ attapulgite (B=Mn, Fe, Co, Ni) nanocomposite for NH3-SCR of NO at low temperature. Journal of Inorganic and Organometallic Polymers. 2017;**27**(1):166-172. DOI: 10.1007/ s10904-017-0683-9

[60] Wallin M, Cruise N, Klement U, Palmqvist A, Skoglundh M. Preparation of Mn, Fe and Co based perovskite catalysts using microemulsions. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2004;**238**(1):27-35. DOI: 10.1016/j.colsurfa.2004.02.019

[61] Takahashi N, Shinjoh H, Iijima T, Suzuki T, Yamazaki K, Yokota K, et al. The new concept 3-way catalyst for automotive lean-burn engine: NOx storage and reduction catalyst. Catalysis Today. 1996;**27**(1):63-69. DOI: 10.1016/0920-5861(95)00173-5

[62] Nova I, Castoldi L, Lietti L, Tronconi E, Forzatti P. On the dynamic behavior of NOx storage/reduction Pt–Ba/Al2O3 catalyst. Catalysis Today. 2002;**75**(1):431-437. DOI: 10.1016/ S0920-5861(02)00093-7

[63] Nova I, Castoldi L, Lietti L, Tronconi E, Forzatti P, Prinetto F, Ghiotti G. NOx adsorption study over Pt–Ba/alumina catalysts: FT-IR and pulse experiments. Journal of Catalysis. 2004;**222**(2):377-388. DOI: 10.1016/j. jcat.2003.11.013

[64] Lietti L, Forzatti P, Nova I, Tronconi E. NOx storage reduction over Pt-Ba/γ-Al2O3 catalyst. Journal of Catalysis. 2001;**204**(1):175-191. DOI: 10.1006/jcat.2001.3370

[65] Lietti L, Nova I, Forzatti P. Role of ammonia in the reduction by hydrogen of NOx stored over Pt–Ba/Al2O3 lean NOx trap catalysts. Journal of Catalysis. 2008;**257**(2):270-282. DOI: 10.1016/j. jcat.2008.05.005

[66] Onrubia-Calvo JA. Perovskites as alternative for NOx storage and reduction systems: formulations, mechanism and optimal control [thesis]. Leioa: Universidad del País Vasco; 2019

[67] You R, Meng M, Zhang J, Zheng L, Hu T, Li X. A noble-metal-free SCR-LNT coupled catalytic system used for high-concentration NOx reduction under lean-burn condition. Catalysis Today. 2019;**327**:347-356. DOI: 10.1016/j. cattod.2018.03.022

[68] Epling WS, Campbell LE, Yezerets A, Currier NW, Parks JE. Overview of the fundamental reactions and degradation mechanisms of NOx storage/reduction catalysts. Catalysis Reviews. 2004;**46**(2):163-245. DOI: 10.1081/CR-200031932

[69] Pereda-Ayo B, De La Torre U, González-Marcos MP,

González-Velasco JR. Influence of ceria loading on the NOx storage and reduction performance of model Pt–Ba/ Al2O3 NSR catalyst. Catalysis Today. 2015;**241**:133-142. DOI: 10.1016/j. cattod.2014.03.044

[70] Chen J, Shen M, Wang X, Qi G, Wang J, Li W. The influence of nonstoichiometry on LaMnO3 perovskite for catalytic NO oxidation. Applied Catalysis B: Environmental. 2013;**134-135**:251-257. DOI: 10.1016/j. apcatb.2013.01.027

[71] Chen J, Shen M, Wang X, Wang J, Su Y, Zhao Z. Catalytic performance of NO oxidation over LaMeO3 (Me=Mn, Fe, Co) perovskite prepared by the sol– gel method. Catalysis Communications. 2013;**37**:105-108. DOI: 10.1016/j. catcom.2013.03.039

[72] Choi SO, Penninger M, Kim CH, Schneider WF, Thompson LT. Experimental and computational investigation of effect of Sr on NO oxidation and oxygen exchange for La1-xSrxCoO3 perovskite catalysts. ACS Catalysis. 2013;**3**(12):2719-2728. DOI: 10.1021/cs400522r

[73] Mars P, van Krevelen DW. Oxidations carried out by means of vanadium oxide catalysts. Chemical Engineering Science. 1954;**3**:41-59. DOI: 10.1016/S0009-2509(54)80005-4

[74] Idriss H, Barteau MA. Active sites on oxides: From single crystals to catalysts. Advances in Catalysis. 2000;**45**:261-331. DOI: 10.1016/S0360-0564(02)45016-X

[75] Białobok B, Trawczyński J, Miśta W, Zawadzki M. Ethanol combustion over strontium- and cerium-doped LaCoO3 catalysts. Applied Catalysis B: Environmental. 2007;**72**(3-4):395-403. DOI: 10.1016/j.apcatb.2006.12.006

[76] Dow W, Huang T. Yttria-stabilized zirconia supported copper oxide catalyst: II. Effect of oxygen vacancy

of support on catalytic activity for CO oxidation. Journal of Catalysis. 1996;**160**(2):171-182. DOI: 10.1006/ jcat.1996.0136

[77] Islam MS, Cherry M, Winch LJ. Defect chemistry of LaBO3 (B = Al, Mn or Co) perovskite-type oxides. Relevance to catalytic and transport behaviour. Journal of the Chemical Society, Faraday Transactions. 1996;**92**(3):479-482. DOI: 10.1039/ FT9969200479

[78] Chien C, Shi J, Huang T. Effect of oxygen vacancy on CO-NO-O2 reaction over yttria-stabilized zirconiasupported copper oxide catalyst. Industrial and Engineering Chemistry Research. 1997;**36**(5):1544-1551. DOI: 10.1006/jcat.1996.0136

[79] Over H. Surface chemistry of ruthenium dioxide in heterogeneous catalysis and electrocatalysis: From fundamental to applied research. Chemical Reviews. 2012;**112**(6): 3356-3426. DOI: 10.1021/cr200247n

[80] Constantinou C, Li W, Qi G, Epling WS. NOX storage and reduction over a perovskite-based lean NOX trap catalyst. Applied Catalysis B: Environmental. 2013;**134-135**:66-74. DOI: 10.1016/j.apcatb.2012.12.034

[81] Qi G, Li W. Pt-free, LaMnO3 based lean NOx trap catalysts. Catalysis Today. 2012;**184**(1):72-77. DOI: 10.1016/j. cattod.2011.11.012

[82] He X, Meng M, He J, Zou Z, Li X, Li Z, et al. A potential substitution of noble metal Pt by perovskite LaCoO3 in ZrTiO4 supported lean-burn NOx trap catalysts. Catalysis Communications. 2010;**12**(3):165-168. DOI: 10.1016/j. catcom.2010.09.016

[83] You R, Zhang Y, Liu D, Meng M, Jiang Z, Zhang S, et al. A series of ceria supported lean-burn NOx trap catalysts LaCoO3/K2CO3/CeO2 using perovskite

**91**

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust…*

Environmental. 2007;**75**(3):157-166. DOI: 10.1016/j.apcatb.2007.04.005

[90] Say Z, Dogac M, Vovk EI, Kalay YE, Kim CH, Li W, et al. Palladium doped perovskite-based NO oxidation catalysts: The role of Pd and B-sites for NOx adsorption behavior via in-situ spectroscopy. Applied Catalysis B: Environmental. 2014;**154-155**:51-61. DOI: 10.1016/j.apcatb.2014.01.038

[91] Zhang R, Alamdari H, Kaliaguine S. Fe-based perovskites substituted by copper and palladium for NO+CO reaction. Journal of Catalysis. 2006;**242**(2):241-253. DOI: 10.1016/j.

[92] Yoon DY, Kim YJ, Lim JH, Cho BK, Hong SB, Nam I, et al. Thermal stability of Pd-containing LaAlO3 perovskite as a modern TWC. Journal of Catalysis. 2015;**330**:71-83. DOI: 10.1016/j.

[93] Li C, Wang C, Lin Y. Pd-integrated lanthanum-transition metal perovskites for methanol partial oxidation. Catalysis Today. 2011;**174**(1):135-140. DOI: 10.1016/j.cattod.2011.01.038

[94] Nishihata Y, Mizuki J, Akao T, Tanaka H, Uenishi M, Kimura M, et al. Self-regeneration of a Pd-perovskite catalyst for automotive emissions control. Nature. 2002;**418**:164. DOI:

[95] Zhou K, Chen H, Tian Q, Hao Z, Shen D. Xu X. Pd-containing perovskitetype oxides used for three-way catalysts.

Journal of Molecular Catalysis A: Chemical. 2002;**189**(2):225-232. DOI: 10.1016/S1381-1169(02)00177-2

[96] Rodríguez GCM, Kelm K, Heikens S, Grünert W, Saruhan B. Pd-integrated perovskites for TWC applications: Synthesis, microstructure

and N2O-sele. Catalysis Today. 2012;**184**(1):184-191. DOI: 10.1016/j.

cattod.2011.12.026

10.1038/nature00893

jcat.2006.05.033

jcat.2015.07.013

*DOI: http://dx.doi.org/10.5772/intechopen.89532*

Engineering Journal. 2015;**260**:357-367.

[84] You R, Zhang Y, Liu D, Meng M, Zheng L, Zhang J, et al. YCeZrO ternary

as active component. Chemical

DOI: 10.1016/j.cej.2014.09.016

oxide solid solution supported nonplatinic lean-burn NOx trap catalysts using LaCoO3 perovskite as active phase. Journal of Physical Chemistry C. 2014;**118**(44):25403- 25420. DOI: 10.1021/jp505601x

[85] Onrubia-Calvo JA, Pereda-Ayo B, De-La-Torre U, González-Velasco JR. Strontium doping and impregnation onto alumina improve the NOx storage and reduction capacity of LaCoO3 perovskites. Catalysis Today. 2019;**333**:208-218. DOI: 10.1016/j.

[86] Li XG, Dong YH, Xian H, Hernández WY, Meng M, Zou HH, et al. De-NOx in alternative lean/ rich atmospheres on La1-xSrxCoO3 perovskites. Energy & Environmental Science. 2011;**4**(9):3351-3354. DOI:

[87] Xian H, Zhang X, Li X, Li L, Zou H, Meng M, et al. BaFeO3-x perovskite: An efficient NOx absorber with a high sulfur tolerance. Journal of Physical

11844-11852. DOI: 10.1021/jp100197c

[88] Dacquin JP, Lancelot C, Dujardin C, Da Costa P, Djega-Mariadassou G, Beaunier P, et al. Influence of preparation methods of LaCoO3 on the catalytic performances in the decomposition of N2O. Applied Catalysis B: Environmental.

2009;**91**(3-4):596-604. DOI: 10.1016/j.

[89] Giraudon JM, Elhachimi A, Wyrwalski F, Siffert S, Aboukaïs A, Lamonier JF, et al. Studies of the activation process over Pd perovskitetype oxides used for catalytic oxidation

of toluene. Applied Catalysis B:

apcatb.2009.06.032

cattod.2018.12.031

10.1039/C1EE01726H

Chemistry C. 2010;**114**(27):

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust… DOI: http://dx.doi.org/10.5772/intechopen.89532*

as active component. Chemical Engineering Journal. 2015;**260**:357-367. DOI: 10.1016/j.cej.2014.09.016

*Perovskite Materials, Devices and Integration*

of support on catalytic activity for CO oxidation. Journal of Catalysis. 1996;**160**(2):171-182. DOI: 10.1006/

[77] Islam MS, Cherry M, Winch LJ. Defect chemistry of LaBO3 (B = Al, Mn or Co) perovskite-type oxides. Relevance to catalytic and transport behaviour. Journal of the Chemical Society, Faraday Transactions. 1996;**92**(3):479-482. DOI: 10.1039/

[78] Chien C, Shi J, Huang T. Effect of oxygen vacancy on CO-NO-O2 reaction over yttria-stabilized zirconiasupported copper oxide catalyst. Industrial and Engineering Chemistry Research. 1997;**36**(5):1544-1551. DOI:

[79] Over H. Surface chemistry of ruthenium dioxide in heterogeneous catalysis and electrocatalysis: From fundamental to applied research. Chemical Reviews. 2012;**112**(6): 3356-3426. DOI: 10.1021/cr200247n

[80] Constantinou C, Li W, Qi G, Epling WS. NOX storage and reduction over a perovskite-based lean NOX trap catalyst. Applied Catalysis B: Environmental. 2013;**134-135**:66-74. DOI: 10.1016/j.apcatb.2012.12.034

[81] Qi G, Li W. Pt-free, LaMnO3 based lean NOx trap catalysts. Catalysis Today. 2012;**184**(1):72-77. DOI: 10.1016/j.

[82] He X, Meng M, He J, Zou Z, Li X, Li Z, et al. A potential substitution of noble metal Pt by perovskite LaCoO3 in ZrTiO4 supported lean-burn NOx trap catalysts. Catalysis Communications. 2010;**12**(3):165-168. DOI: 10.1016/j.

[83] You R, Zhang Y, Liu D, Meng M, Jiang Z, Zhang S, et al. A series of ceria supported lean-burn NOx trap catalysts LaCoO3/K2CO3/CeO2 using perovskite

cattod.2011.11.012

catcom.2010.09.016

jcat.1996.0136

FT9969200479

10.1006/jcat.1996.0136

González-Velasco JR. Influence of ceria loading on the NOx storage and reduction performance of model Pt–Ba/ Al2O3 NSR catalyst. Catalysis Today. 2015;**241**:133-142. DOI: 10.1016/j.

[70] Chen J, Shen M, Wang X, Qi G, Wang J, Li W. The influence of nonstoichiometry on LaMnO3 perovskite for catalytic NO oxidation. Applied Catalysis B: Environmental. 2013;**134-135**:251-257. DOI: 10.1016/j.

[71] Chen J, Shen M, Wang X, Wang J, Su Y, Zhao Z. Catalytic performance of NO oxidation over LaMeO3 (Me=Mn, Fe, Co) perovskite prepared by the sol– gel method. Catalysis Communications.

Kim CH, Schneider WF, Thompson LT. Experimental and computational investigation of effect of Sr on NO oxidation and oxygen exchange for La1-xSrxCoO3 perovskite catalysts. ACS Catalysis. 2013;**3**(12):2719-2728. DOI:

[74] Idriss H, Barteau MA. Active sites on oxides: From single crystals to catalysts. Advances in Catalysis. 2000;**45**:261-331. DOI: 10.1016/S0360-0564(02)45016-X

[75] Białobok B, Trawczyński J, Miśta W, Zawadzki M. Ethanol combustion over strontium- and cerium-doped LaCoO3 catalysts. Applied Catalysis B: Environmental. 2007;**72**(3-4):395-403. DOI: 10.1016/j.apcatb.2006.12.006

[76] Dow W, Huang T. Yttria-stabilized zirconia supported copper oxide catalyst: II. Effect of oxygen vacancy

2013;**37**:105-108. DOI: 10.1016/j.

[72] Choi SO, Penninger M,

[73] Mars P, van Krevelen DW. Oxidations carried out by means of vanadium oxide catalysts. Chemical Engineering Science. 1954;**3**:41-59. DOI: 10.1016/S0009-2509(54)80005-4

cattod.2014.03.044

apcatb.2013.01.027

catcom.2013.03.039

10.1021/cs400522r

**90**

[84] You R, Zhang Y, Liu D, Meng M, Zheng L, Zhang J, et al. YCeZrO ternary oxide solid solution supported nonplatinic lean-burn NOx trap catalysts using LaCoO3 perovskite as active phase. Journal of Physical Chemistry C. 2014;**118**(44):25403- 25420. DOI: 10.1021/jp505601x

[85] Onrubia-Calvo JA, Pereda-Ayo B, De-La-Torre U, González-Velasco JR. Strontium doping and impregnation onto alumina improve the NOx storage and reduction capacity of LaCoO3 perovskites. Catalysis Today. 2019;**333**:208-218. DOI: 10.1016/j. cattod.2018.12.031

[86] Li XG, Dong YH, Xian H, Hernández WY, Meng M, Zou HH, et al. De-NOx in alternative lean/ rich atmospheres on La1-xSrxCoO3 perovskites. Energy & Environmental Science. 2011;**4**(9):3351-3354. DOI: 10.1039/C1EE01726H

[87] Xian H, Zhang X, Li X, Li L, Zou H, Meng M, et al. BaFeO3-x perovskite: An efficient NOx absorber with a high sulfur tolerance. Journal of Physical Chemistry C. 2010;**114**(27): 11844-11852. DOI: 10.1021/jp100197c

[88] Dacquin JP, Lancelot C, Dujardin C, Da Costa P, Djega-Mariadassou G, Beaunier P, et al. Influence of preparation methods of LaCoO3 on the catalytic performances in the decomposition of N2O. Applied Catalysis B: Environmental. 2009;**91**(3-4):596-604. DOI: 10.1016/j. apcatb.2009.06.032

[89] Giraudon JM, Elhachimi A, Wyrwalski F, Siffert S, Aboukaïs A, Lamonier JF, et al. Studies of the activation process over Pd perovskitetype oxides used for catalytic oxidation of toluene. Applied Catalysis B:

Environmental. 2007;**75**(3):157-166. DOI: 10.1016/j.apcatb.2007.04.005

[90] Say Z, Dogac M, Vovk EI, Kalay YE, Kim CH, Li W, et al. Palladium doped perovskite-based NO oxidation catalysts: The role of Pd and B-sites for NOx adsorption behavior via in-situ spectroscopy. Applied Catalysis B: Environmental. 2014;**154-155**:51-61. DOI: 10.1016/j.apcatb.2014.01.038

[91] Zhang R, Alamdari H, Kaliaguine S. Fe-based perovskites substituted by copper and palladium for NO+CO reaction. Journal of Catalysis. 2006;**242**(2):241-253. DOI: 10.1016/j. jcat.2006.05.033

[92] Yoon DY, Kim YJ, Lim JH, Cho BK, Hong SB, Nam I, et al. Thermal stability of Pd-containing LaAlO3 perovskite as a modern TWC. Journal of Catalysis. 2015;**330**:71-83. DOI: 10.1016/j. jcat.2015.07.013

[93] Li C, Wang C, Lin Y. Pd-integrated lanthanum-transition metal perovskites for methanol partial oxidation. Catalysis Today. 2011;**174**(1):135-140. DOI: 10.1016/j.cattod.2011.01.038

[94] Nishihata Y, Mizuki J, Akao T, Tanaka H, Uenishi M, Kimura M, et al. Self-regeneration of a Pd-perovskite catalyst for automotive emissions control. Nature. 2002;**418**:164. DOI: 10.1038/nature00893

[95] Zhou K, Chen H, Tian Q, Hao Z, Shen D. Xu X. Pd-containing perovskitetype oxides used for three-way catalysts. Journal of Molecular Catalysis A: Chemical. 2002;**189**(2):225-232. DOI: 10.1016/S1381-1169(02)00177-2

[96] Rodríguez GCM, Kelm K, Heikens S, Grünert W, Saruhan B. Pd-integrated perovskites for TWC applications: Synthesis, microstructure and N2O-sele. Catalysis Today. 2012;**184**(1):184-191. DOI: 10.1016/j. cattod.2011.12.026

[97] Zhao D, Gao Z, Xian H, Xing L, Yang Y, Tian Y, et al. Addition of Pd on La0.7Sr0.3CoO3 perovskite to enhance catalytic removal of NOx. Industrial and Engineering Chemistry Research. 2018;**57**(2):521-531. DOI: 10.1021/acs. iecr.7b04399

[98] Ye J, Yu Y, Meng M, Jiang Z, Ding T, Zhang S, et al. Highly efficient NOx purification in alternating lean/ rich atmospheres over non-platinic mesoporous perovskite-based catalyst K/LaCoO3. Catalysis Science & Technology. 2013;**3**(8):1915-1918. DOI: 10.1039/C3CY00155E

[99] Wen W, Wang X, Jin S, Wang R. LaCoO3 perovskite in Pt/LaCoO3/K/ Al2O3 for the improvement of NOx storage and reduction performances. RSC Advances. 2016;**6**(78):74046- 74052. DOI: 10.1039/C6RA18273A

[100] Ueda A, Yamada Y, Katsuki M, Kiyobayashi T, Xu Q, Kuriyama N. Perovskite catalyst (La, Ba)(Fe, Nb, Pd)O3 applicable to NOx storage and reduction system. Catalysis Communications. 2009;**11**(1):34-37. DOI: 10.1016/j.catcom.2009.08.008

[101] Hodjati S, Petit C, Pitchon V, Kiennemann A. Absorption/desorption of NOx process on perovskites: Impact of SO2 on the storage capacity of BaSnO3 and strategy to develop thioresistance. Applied Catalysis B: Environmental. 2001;**30**(3):247-257. DOI: 10.1016/ S0926-3373(00)00249-6

[102] Hodjati S, Vaezzadeh K, Petit C, Pitchon V, Kiennemann A. Absorption/ desorption of NOx process on perovskites: Performances to remove NOx from a lean exhaust gas. Applied Catalysis B: Environmental. 2000;**26**(1):5-16. DOI: 10.1016/ S0926-3373(99)00143-5

[103] Xian H, Zhang X, Li X, Zou H, Meng M, Zou Z, et al. Effect of the calcination conditions on the NOx

storage behavior of the perovskite BaFeO3−x catalysts. Catalysis Today. 2010;**158**(3):215-219. DOI: 10.1016/j. cattod.2010.03.026

[104] Xian H, Li F, Li X, Zhang X, Meng M, Zhang T, et al. Influence of preparation conditions to structure property, NOx and SO2 sorption behavior of the BaFeO3−x perovskite catalyst. Fuel Processing Technology. 2011;**92**(9):1718-1724. DOI: 10.1016/j. fuproc.2011.04.021

[105] Li X, Chen C, Liu C, Xian H, Guo L, Lv J, et al. Pd-doped perovskite: An effective catalyst for removal of NOx from lean-burn exhausts with high sulfur resistance. ACS Catalysis. 2013;**3**(6):1071-1075. DOI: 10.1021/ cs400136t

[106] Ma A, Wang S, Liu C, Xian H, Ding Q, Guo L, et al. Effects of Fe dopants and residual carbonates on the catalytic activities of the perovskitetype La0.7Sr0.3Co1−xFexO3 NOx storage catalyst. Applied Catalysis B: Environmental. 2014;**146**:24-34. DOI: 10.1016/j.apcatb.2013.06.005

[107] Wang X, Qi X, Chen Z, Jiang L, Wang R, Wei K. Studies on SO2 tolerance and regeneration over perovskitetype LaCo1-xPtxO3 in NOx storage and reduction. Journal of Physical Chemistry C. 2014;**118**(25):13743-13751. DOI: 10.1021/jp5044255

[108] Minami, Toshitake (Kanagawa, JP) 2009. Device for purifying exhaust gas of a diesel engine United States 20090250041 http://www. freepatentsonline.com/y2009/0250041. html

[109] Sakurai K. Exhaust purifying system for internal combustion engine. US Patent Appl. 2011/0138783 A1 (16-06-2011)

[110] De La Torre U, Urrutxua M, Pereda-Ayo B, González-Velasco JR.

**93**

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust…*

Chansai S. Regeneration mechanism of a lean NOx trap (LNT) catalyst in the presence of NO investigated using isotope labelling techniques. Journal of Catalysis. 2012;**285**(1):177-186. DOI:

10.1016/j.jcat.2011.09.028

*DOI: http://dx.doi.org/10.5772/intechopen.89532*

On the Cu species in Cu/beta catalysts related to DeNOx performance of coupled NSR-SCR technology using sequential monoliths and dual-layer monolithic catalysts. Catalysis Today. 2016;**273**:72-82. DOI: 10.1016/j.

[111] De-La-Torre U, Pereda-Ayo B, Moliner M, González-Velasco JR, Corma A. Cu-zeolite catalysts for NOx removal by selective catalytic reduction with NH3 and coupled to NO storage/ reduction monolith in diesel engine exhaust after treatment systems. Applied Catalysis B: Environmental.

[112] Pereda-Ayo B, Duraiswami D, Delgado JJ, López-Fonseca R, Calvino JJ, Bernal S, et al. Tuning operational conditions for efficient NOx storage and reduction over a Pt–Ba/Al2O3 monolith catalyst. Applied Catalysis B: Environmental. 2010;**96**(3-4):329-337

[113] Pereda-Ayo B, Duraiswami D, González-Marcos JA, González-

[114] Pereda-Ayo B, Duraiswami D, González-Velasco JR. Control of NOx storage and reduction in NSR bed for designing combined NSR–SCR systems. Catalysis Today. 2011;**172**(1):66-72. DOI:

10.1016/j.cattod.2011.01.043

10.1016/j.jcat.2006.11.008

[116] Pereda-Ayo B, González-Velasco JR, Burch R, Hardacre C,

[115] Cumaranatunge L, Mulla SS, Yezerets A, Currier NW, Delgass WN, Ribeiro FH. Ammonia is a hydrogen carrier in the regeneration of Pt/BaO/ Al2O3 NOx traps with H2. Journal of Catalysis. 2007;**246**(1):29-34. DOI:

Velasco JR. Performance of NOx storagereduction catalyst in the temperaturereductant concentration domain by response surface methodology. Chemical Engineering Journal. 2011;**169**(1-3):58-67. DOI: 10.1016/j.

cattod.2016.02.054

2016;**187**:419-427

cej.2011.02.052

*Perovskite-Based Formulations as Rival Platinum Catalysts for NOx Removal in Diesel Exhaust… DOI: http://dx.doi.org/10.5772/intechopen.89532*

On the Cu species in Cu/beta catalysts related to DeNOx performance of coupled NSR-SCR technology using sequential monoliths and dual-layer monolithic catalysts. Catalysis Today. 2016;**273**:72-82. DOI: 10.1016/j. cattod.2016.02.054

*Perovskite Materials, Devices and Integration*

[97] Zhao D, Gao Z, Xian H, Xing L, Yang Y, Tian Y, et al. Addition of Pd on La0.7Sr0.3CoO3 perovskite to enhance catalytic removal of NOx. Industrial and Engineering Chemistry Research. 2018;**57**(2):521-531. DOI: 10.1021/acs.

storage behavior of the perovskite BaFeO3−x catalysts. Catalysis Today. 2010;**158**(3):215-219. DOI: 10.1016/j.

[104] Xian H, Li F, Li X, Zhang X, Meng M, Zhang T, et al. Influence of preparation conditions to structure property, NOx and SO2 sorption behavior of the BaFeO3−x perovskite catalyst. Fuel Processing Technology. 2011;**92**(9):1718-1724. DOI: 10.1016/j.

[105] Li X, Chen C, Liu C, Xian H, Guo L, Lv J, et al. Pd-doped perovskite: An effective catalyst for removal of NOx from lean-burn exhausts with high sulfur resistance. ACS Catalysis. 2013;**3**(6):1071-1075. DOI: 10.1021/

[106] Ma A, Wang S, Liu C, Xian H, Ding Q, Guo L, et al. Effects of Fe dopants and residual carbonates on the catalytic activities of the perovskitetype La0.7Sr0.3Co1−xFexO3 NOx

storage catalyst. Applied Catalysis B: Environmental. 2014;**146**:24-34. DOI:

[107] Wang X, Qi X, Chen Z, Jiang L, Wang R, Wei K. Studies on SO2 tolerance and regeneration over perovskitetype LaCo1-xPtxO3 in NOx storage and reduction. Journal of Physical Chemistry C. 2014;**118**(25):13743-13751.

[108] Minami, Toshitake (Kanagawa, JP) 2009. Device for purifying exhaust gas of a diesel engine United States 20090250041 http://www. freepatentsonline.com/y2009/0250041.

[109] Sakurai K. Exhaust purifying system for internal combustion engine. US Patent Appl. 2011/0138783 A1

[110] De La Torre U, Urrutxua M, Pereda-Ayo B, González-Velasco JR.

10.1016/j.apcatb.2013.06.005

DOI: 10.1021/jp5044255

html

(16-06-2011)

cattod.2010.03.026

fuproc.2011.04.021

cs400136t

[98] Ye J, Yu Y, Meng M, Jiang Z, Ding T, Zhang S, et al. Highly efficient NOx purification in alternating lean/ rich atmospheres over non-platinic mesoporous perovskite-based catalyst K/LaCoO3. Catalysis Science &

Technology. 2013;**3**(8):1915-1918. DOI:

[99] Wen W, Wang X, Jin S, Wang R. LaCoO3 perovskite in Pt/LaCoO3/K/ Al2O3 for the improvement of NOx storage and reduction performances. RSC Advances. 2016;**6**(78):74046- 74052. DOI: 10.1039/C6RA18273A

[100] Ueda A, Yamada Y, Katsuki M, Kiyobayashi T, Xu Q, Kuriyama N. Perovskite catalyst (La, Ba)(Fe, Nb, Pd)O3 applicable to NOx storage and reduction system. Catalysis Communications. 2009;**11**(1):34-37. DOI: 10.1016/j.catcom.2009.08.008

[101] Hodjati S, Petit C, Pitchon V, Kiennemann A. Absorption/desorption of NOx process on perovskites: Impact of SO2 on the storage capacity of BaSnO3 and strategy to develop thioresistance. Applied Catalysis B: Environmental. 2001;**30**(3):247-257. DOI: 10.1016/

[102] Hodjati S, Vaezzadeh K, Petit C, Pitchon V, Kiennemann A. Absorption/

[103] Xian H, Zhang X, Li X, Zou H, Meng M, Zou Z, et al. Effect of the calcination conditions on the NOx

desorption of NOx process on perovskites: Performances to remove

NOx from a lean exhaust gas. Applied Catalysis B: Environmental. 2000;**26**(1):5-16. DOI: 10.1016/ S0926-3373(99)00143-5

S0926-3373(00)00249-6

iecr.7b04399

10.1039/C3CY00155E

**92**

[111] De-La-Torre U, Pereda-Ayo B, Moliner M, González-Velasco JR, Corma A. Cu-zeolite catalysts for NOx removal by selective catalytic reduction with NH3 and coupled to NO storage/ reduction monolith in diesel engine exhaust after treatment systems. Applied Catalysis B: Environmental. 2016;**187**:419-427

[112] Pereda-Ayo B, Duraiswami D, Delgado JJ, López-Fonseca R, Calvino JJ, Bernal S, et al. Tuning operational conditions for efficient NOx storage and reduction over a Pt–Ba/Al2O3 monolith catalyst. Applied Catalysis B: Environmental. 2010;**96**(3-4):329-337

[113] Pereda-Ayo B, Duraiswami D, González-Marcos JA, González-Velasco JR. Performance of NOx storagereduction catalyst in the temperaturereductant concentration domain by response surface methodology. Chemical Engineering Journal. 2011;**169**(1-3):58-67. DOI: 10.1016/j. cej.2011.02.052

[114] Pereda-Ayo B, Duraiswami D, González-Velasco JR. Control of NOx storage and reduction in NSR bed for designing combined NSR–SCR systems. Catalysis Today. 2011;**172**(1):66-72. DOI: 10.1016/j.cattod.2011.01.043

[115] Cumaranatunge L, Mulla SS, Yezerets A, Currier NW, Delgass WN, Ribeiro FH. Ammonia is a hydrogen carrier in the regeneration of Pt/BaO/ Al2O3 NOx traps with H2. Journal of Catalysis. 2007;**246**(1):29-34. DOI: 10.1016/j.jcat.2006.11.008

[116] Pereda-Ayo B, González-Velasco JR, Burch R, Hardacre C, Chansai S. Regeneration mechanism of a lean NOx trap (LNT) catalyst in the presence of NO investigated using isotope labelling techniques. Journal of Catalysis. 2012;**285**(1):177-186. DOI: 10.1016/j.jcat.2011.09.028

**Chapter 6**

**Abstract**

transport features.

**1. Introduction**

of our time.

**95**

perovskite synthesis, transport properties

*and Konstantin Petrov*

Perovskite-Based Materials

*Mirela Dragan, Stanica Enache, Mihai Varlam*

The role of energy in modern society is fundamental. Constraints due to the emissions of air pollutants from the excessive use of fossil fuels have increased dramatically in the last years. Over the years various devices and systems have been developed to transform energy from forms supplied by nature to forms that can be used by people. Another issue is to absorb energy generated at one time and to discharge it to supply power at a later time, what is called energy storage. This is also a matter to focus when it comes to searching for solutions of energy problems. Perovskites are promising key materials for energy applications, and in this chapter is a literature review summarizing the reported progress in energy applications of perovskite-type ceramic materials. To understand the fundamental nature of structure–property relationships, defect chemistry plays an important role. This paper, a mini-review, briefly describes from available literature and summarizes accordingly. It is focused on perovskite crystal structures, perovskite materials for solid oxide fuel cells, perovskite electrocatalyst and photocatalysts, and perovskite

**Keywords:** perovskite, perovskite crystal structure, defect chemistry,

*more energy* to allow global living standards to continue to improve.

There is going to be huge demand for energy. The growing population and the growing of industrialization will increase the demand for energy. The world needs

Currently most of our energy comes from fossil fuels, which originated from deep within the Earth's crust. This had disastrous effects on the planet because the burning of coal, oil, and gas has been linked to the rising levels of greenhouse gases on the Earth's atmosphere, generating climate change. The global energy landscape requires improvements. There is a slow going on transition to a more sustainable energy system. Not only to meet the need of rising energy demand but also in terms of policy, reducing carbon emission energy systems is the biggest challenges

Along with these challenges come opportunities—and that is what makes this a really exciting time for material science with respect to efficient and cost-effective energy conversion and energy storage. The process of changing energy from one

for Energy Applications

## **Chapter 6**

## Perovskite-Based Materials for Energy Applications

*Mirela Dragan, Stanica Enache, Mihai Varlam and Konstantin Petrov*

## **Abstract**

The role of energy in modern society is fundamental. Constraints due to the emissions of air pollutants from the excessive use of fossil fuels have increased dramatically in the last years. Over the years various devices and systems have been developed to transform energy from forms supplied by nature to forms that can be used by people. Another issue is to absorb energy generated at one time and to discharge it to supply power at a later time, what is called energy storage. This is also a matter to focus when it comes to searching for solutions of energy problems. Perovskites are promising key materials for energy applications, and in this chapter is a literature review summarizing the reported progress in energy applications of perovskite-type ceramic materials. To understand the fundamental nature of structure–property relationships, defect chemistry plays an important role. This paper, a mini-review, briefly describes from available literature and summarizes accordingly. It is focused on perovskite crystal structures, perovskite materials for solid oxide fuel cells, perovskite electrocatalyst and photocatalysts, and perovskite transport features.

**Keywords:** perovskite, perovskite crystal structure, defect chemistry, perovskite synthesis, transport properties

## **1. Introduction**

There is going to be huge demand for energy. The growing population and the growing of industrialization will increase the demand for energy. The world needs *more energy* to allow global living standards to continue to improve.

Currently most of our energy comes from fossil fuels, which originated from deep within the Earth's crust. This had disastrous effects on the planet because the burning of coal, oil, and gas has been linked to the rising levels of greenhouse gases on the Earth's atmosphere, generating climate change. The global energy landscape requires improvements. There is a slow going on transition to a more sustainable energy system. Not only to meet the need of rising energy demand but also in terms of policy, reducing carbon emission energy systems is the biggest challenges of our time.

Along with these challenges come opportunities—and that is what makes this a really exciting time for material science with respect to efficient and cost-effective energy conversion and energy storage. The process of changing energy from one

form to another is energy conversion, and energy storage is the capture of energy produced at one time for use at a later time.

the Ural Mountains in Russia back in 1893. During that time, he identified perovskite, a naturally occurring oxide species, with the chemical formula CaTiO3 and named it after Russian mineralogist Count Lev Alekseyevich von Perovski [25]. The ideal perovskite-type structure is cubic with space group Pm3m [26]. The positive charge B-type cations are occupying the centers of corner-shared octahedra of negative charge X-type anions such as oxygen halides, sulfides, or nitrides, and positive charge A-type cations are filling the resulting interstices. We restrict this

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

*The orthorhombic phase of perovskite. Green spheres represent A cations, blue spheres represent B cations, and*

*The tetragonal phase of perovskite. Green spheres represent A cations, blue spheres represent B cations, and red*

**Figure 2.**

**Figure 3.**

**97**

*spheres represent oxygen anions.*

*red spheres represent oxygen anions.*

This work aims to provide an overview, based on available literature, of perovskite materials for energy applications and will focus especially on solid oxide fuel cells for efficient power generation from fuels and electrocatalysts for oxygen reduction reaction, oxygen evolution reaction, as well as on the defect chemistry in general of such materials. A large number of articles related on this topic have been published in the past decades. Unfortunately, it is not possible to cover all the aspects and references in the literature.

Due to their properties, the perovskite materials are of considerable technological importance covering a very broad range of practical applications. Notable is the discovery in the 1940s of the ferroelectric properties of barium titanate (BaTiO3) used in electronics for capacitors and transducers [1]. In the mid-1980s, the first high-temperature superconductor was discovered, lanthanum barium copper oxide and, in 1987 Nobel Prize in physics, was awarded for this discovery [2]. As of 2012, perovskites have been identified as possible inexpensive base materials for highefficiency commercial photovoltaics, and perovskites also have optoelectronic properties such as strong light absorption and facilitated charge transport [3]. Some of perovskites' typical properties are ferromagnetism [4], piezoelectricity [5, 6], electrical conductivity [7, 8], superconductivity [9, 10], ion conductivity [11, 12], magnetism [13, 14], catalytic properties [15, 16], electrode materials [17, 18], and optical [19, 20].

This work will describe their defect chemistry which plays an important role in energy applications where the transport properties are the main players. Their defect chemistry is responsible for properties like ionic conductivity [21], mixed conductivity [22], proton conductivity [23], and catalytic conductivity [24] which make perovskite being used for solid oxide fuel cells (SOFC), electrolyte, SOFC electrode, and catalyst.

## **2. Perovskites and related structures**

The perovskite structure is adopted by many compounds residing on the generic formula ABX3, the same type of crystal structure as calcium titanium oxide (CaTiO3), constituting the family of perovskite compounds. We owe the discovery of perovskite to Gustav Rose, a German mineralogist who performed the studies in

#### **Figure 1.**

*Cubic perovskite unit cell. Green spheres represent A cations, blue spheres represent B cations, and red spheres represent oxygen anions forming an octahedron. (a). In the perovskite structure with the large cation at the cube center, the small cations are on the corners, and the anions are located at the midpoint of each edge. (b). It emphasizes the octahedral coordination of the small cation.*

## *Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

the Ural Mountains in Russia back in 1893. During that time, he identified perovskite, a naturally occurring oxide species, with the chemical formula CaTiO3 and named it after Russian mineralogist Count Lev Alekseyevich von Perovski [25].

The ideal perovskite-type structure is cubic with space group Pm3m [26]. The positive charge B-type cations are occupying the centers of corner-shared octahedra of negative charge X-type anions such as oxygen halides, sulfides, or nitrides, and positive charge A-type cations are filling the resulting interstices. We restrict this

#### **Figure 2.**

form to another is energy conversion, and energy storage is the capture of energy

This work aims to provide an overview, based on available literature, of perovskite materials for energy applications and will focus especially on solid oxide fuel cells for efficient power generation from fuels and electrocatalysts for oxygen reduction reaction, oxygen evolution reaction, as well as on the defect chemistry in general of such materials. A large number of articles related on this topic have been published in the past decades. Unfortunately, it is not possible to cover all the

Due to their properties, the perovskite materials are of considerable technological importance covering a very broad range of practical applications. Notable is the discovery in the 1940s of the ferroelectric properties of barium titanate (BaTiO3) used in electronics for capacitors and transducers [1]. In the mid-1980s, the first high-temperature superconductor was discovered, lanthanum barium copper oxide and, in 1987 Nobel Prize in physics, was awarded for this discovery [2]. As of 2012, perovskites have been identified as possible inexpensive base materials for highefficiency commercial photovoltaics, and perovskites also have optoelectronic properties such as strong light absorption and facilitated charge transport [3]. Some of perovskites' typical properties are ferromagnetism [4], piezoelectricity [5, 6], electrical conductivity [7, 8], superconductivity [9, 10], ion conductivity [11, 12], magnetism [13, 14], catalytic properties [15, 16], electrode materials [17, 18], and

This work will describe their defect chemistry which plays an important role in

The perovskite structure is adopted by many compounds residing on the generic

(CaTiO3), constituting the family of perovskite compounds. We owe the discovery of perovskite to Gustav Rose, a German mineralogist who performed the studies in

*Cubic perovskite unit cell. Green spheres represent A cations, blue spheres represent B cations, and red spheres represent oxygen anions forming an octahedron. (a). In the perovskite structure with the large cation at the cube center, the small cations are on the corners, and the anions are located at the midpoint of each edge. (b). It*

formula ABX3, the same type of crystal structure as calcium titanium oxide

energy applications where the transport properties are the main players. Their defect chemistry is responsible for properties like ionic conductivity [21], mixed conductivity [22], proton conductivity [23], and catalytic conductivity [24] which make perovskite being used for solid oxide fuel cells (SOFC), electrolyte, SOFC

produced at one time for use at a later time.

*Perovskite Materials, Devices and Integration*

aspects and references in the literature.

optical [19, 20].

**Figure 1.**

**96**

electrode, and catalyst.

**2. Perovskites and related structures**

*emphasizes the octahedral coordination of the small cation.*

*The orthorhombic phase of perovskite. Green spheres represent A cations, blue spheres represent B cations, and red spheres represent oxygen anions.*

### **Figure 3.**

*The tetragonal phase of perovskite. Green spheres represent A cations, blue spheres represent B cations, and red spheres represent oxygen anions.*

<sup>t</sup> <sup>¼</sup> ð Þ rA <sup>þ</sup> rO ffiffi 2 <sup>p</sup> ð Þ rB <sup>þ</sup> rO

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

Cations with large ionic radius are occupying A sites, and cations with smaller ionic radius are occupying B sites. A and O form cubic closest packing, and B is in the octahedral voids in the packing. In an ideal structure, where the atoms are

*The Aurivillius n = 1 structure. Green spheres represent A cations, blue spheres represent B cations, and red*

**Figure 5.**

**99**

*spheres represent oxygen anions.*

(1)

**Figure 4.**

*The Ruddlesden-Popper phases. Green spheres represent A cations, blue spheres represent B cations, and red spheres represent oxygen anions.*

study to the oxide perovskites. In **Figure 1a**, alternative ways to view the perovskite structure are displayed: the cubic perovskite unit cell. **Figure 1b** emphasizes the octahedral coordination of the small cation. Green spheres represent A cations, blue spheres represent B cations, and red spheres represent oxygen anions forming an octahedron. Most perovskites are distorted and do not have the ideal undistorted cubic structure. Few perovskite compounds actually form the ideal cubic structure. The mineral perovskite itself, calcium titanate CaTiO3, is an orthorhombic distortion of the basic structure; strontium titanate SrTiO3 is often used as the prototype.

The equation determined by Goldschmidt correlates geometrically crystal structures in terms of the ionic packing using the Goldschmidt's tolerance factor *t* [27]. Favorable for cubic perovskite structure is the tolerance factor having values between 0.8 and 1; otherwise the ideal cubic structure is a distorted structure. Empirical mathematical expression involving the unit cell length ratio, here rA, rB, and rO, is the ionic radii for A, B, and O, respectively; t is given as

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

$$\mathbf{t} = \frac{(\mathbf{r}\_{\text{A}} + \mathbf{r}\_{\text{O}})}{\sqrt{2}(\mathbf{r}\_{\text{B}} + \mathbf{r}\_{\text{O}})} \tag{1}$$

Cations with large ionic radius are occupying A sites, and cations with smaller ionic radius are occupying B sites. A and O form cubic closest packing, and B is in the octahedral voids in the packing. In an ideal structure, where the atoms are

study to the oxide perovskites. In **Figure 1a**, alternative ways to view the perovskite structure are displayed: the cubic perovskite unit cell. **Figure 1b** emphasizes the octahedral coordination of the small cation. Green spheres represent A cations, blue spheres represent B cations, and red spheres represent oxygen anions forming an octahedron. Most perovskites are distorted and do not have the ideal undistorted cubic structure. Few perovskite compounds actually form the ideal cubic structure.

*The Ruddlesden-Popper phases. Green spheres represent A cations, blue spheres represent B cations, and red*

The equation determined by Goldschmidt correlates geometrically crystal structures in terms of the ionic packing using the Goldschmidt's tolerance factor *t* [27]. Favorable for cubic perovskite structure is the tolerance factor having values between 0.8 and 1; otherwise the ideal cubic structure is a distorted structure. Empirical mathematical expression involving the unit cell length ratio, here rA, rB,

The mineral perovskite itself, calcium titanate CaTiO3, is an orthorhombic distortion of the basic structure; strontium titanate SrTiO3 is often used as the

and rO, is the ionic radii for A, B, and O, respectively; t is given as

prototype.

**98**

**Figure 4.**

*spheres represent oxygen anions.*

*Perovskite Materials, Devices and Integration*

simply bonding to one another, the B-O distance is equal to a/2, whereas the A-O distance is equal to (a/√2) where a = length of unit cell.

The formation of a point defect can be considered as a chemical reaction. At constant temperature, T, and pressure, p, the reaction is carried on in the direction

where H is the enthalpy, U is the internal energy, S is the entropy, and V is the

The change in free energy for the formation of n independent defects can be

In the above equation, the configurational entropy *Δ<sup>f</sup> Sc* is the part of the entropy change associated with randomly distributing n defect in the material. For a single defect, the formation free energy *ΔfG* is independent of the number of defects and

The point defects are a nonstoichiometric perturbation of the ideal lattice having or not electrically charge. Materials can also be prepared in such a way as to

ries of intrinsic defects are Schottky disorder and Frenkel disorder.

There are two main categories for point defects: intrinsic defects and extrinsic defects. The intrinsic defects are internal to the crystal. The extrinsic defects are created when an impurity atom or ion is inserted into the lattice. The main catego-

The Schottky disordering mechanism presumes that atoms leave their sites in

A vacancy is formed if an atom is not present on the site that it should occupy in a perfect crystal. By removing one atom from the chemical formula of perovskite, a set of vacancies called Schottky defect is created, which is the removal of an oxygen atom. Oxygen ion has a charged of �2. The defect left behind after removal, a charge of +2, for an oxygen atom will be *VÖ* in Kröger-Vink notation. The following

V indicates a vacancy, the subscript O indicates the oxygen host site, and super-

An interstitial is an ion situated on any site that would be unoccupied in a perfect crystal. The interstitial is denoted by a subscript *i*, in Kröger-Vink notation. Frenkel defects deal with the displacement of the ions from its sites to interstitial sites. When an ion is substituted with an ion of different valence, another type of

the crystal bulk and rebuild the crystal lattice on the surface. As a result, the vacancies are formed in both cation and anion sublattices. According to the Frenkel mechanism, an atom moves from its regular site to the nearest interstitial position; hence, two types of defect are formed in the crystal, namely, the vacancy and the

equation is written for the creation of oxygen vacancy, Schottky disorder:

O<sup>X</sup> <sup>O</sup> <sup>¼</sup> <sup>1</sup> 2

script denoted by two dots is the defect charge of +2.

point defect is created, called substitutional defect.

G ¼ U þ pV � TS ¼ H � TS (2)

H ¼ U þ pV (3)

ΔG ¼ nΔfG � TΔfSc (4)

ΔfG ¼ ΔfU þ pΔfV � TΔfS (5)

O2 þ VÖ þ 2e<sup>0</sup> (6)

that lowers the Gibbs free energy as follows:

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

volume. The enthalpy H is defined as

written as follows:

can be written as follows:

increase the number of defects.

interstitial atom.

**101**

The orthorhombic (**Figure 2**) and tetragonal (**Figure 3**) phases are the most common non-cubic variants [26] with octahedral distortions and translational A site offsets. As previously mentioned, green spheres represent A cations, blue spheres represent B cations, and red spheres represent oxygen anions.

Perovskites allow chemical tailoring because of the wide range of ions and valences which they can accommodate. By suitable formulation many valuable properties can be tailored. One interesting quality of perovskites is that they can accommodate more than one element for both A- and B sites constituting complex perovskites. These can be represented as (A1 1–xA2 x)BO3, A(B<sup>1</sup> 1–xB<sup>2</sup> x)O3. Substitutional aliovalent cations residing on the host cation sites generate oxygen vacancies. Furthermore for the B site, the element of transition metal can be in different oxidation states A(B'xB"y)O3, where x + y = 1. Aliovalent substitutions require a charge compensation mechanism because the ionic compound must be neutral. Therefore, either ion vacancies are created or one of the metals is partially or fully reduced or oxidized.

Another interesting and useful to deal with is the complex set of phase relationships. These are useful in such materials because they are sensitive to external conditions, including temperature, pressure, strain, and composition [28].

The perovskite structure also lends itself to the building of superstructures as seen in **Figure 4**. The Ruddlesden-Popper phases are a series of structures consisting of sequences of max 3 n; perovskite blocks are separated by a rock-salt structure block. The first member of the Ruddlesden-Popper series is A2BO4 or ABO3-AO which is isostructural with potassium tetrafluoridenickelate (II) K2NiF4, the prototype structure.

A second family of superstructures are the Aurivillius phases (**Figure 5**) [29]. This is represented by the general formula (Bi2O2)(An1BnO3n+1), where A is a large monovalent, divalent, or trivalent 12-coordinate cation and B is a small trivalent, pentavalent, or hexavalent metallic 6-coordinate cation. Basically, their structure is built by alternating layers of [Bi2O2]2 <sup>+</sup> and perovskite blocks (An–1BnO3n+1)2 that contain a layer of octahedral B sites.

Various synthesis methods have been developed for the preparation of perovskite materials while managing efficiently the environmentally friendly processing in conjunction with phase structure tailored to the needed properties. Small changes in the crystal will have a large impact on functional properties, crystallinity, and stability. Among these techniques, dry ways like solid-state reaction mechanochemical processing or wet routes like sol–gel and microwave methods are widely used.

## **3. Perovskite defect chemistry**

In crystalline state an array of atoms is regularly repeated in three dimensions. This construction leads to a perfect crystalline solid with all atoms present and located in their ideal positions. However, a zero entropy is needed for the perfect crystalline state to exist. Above absolute zero temperature is a probability that defects from ideality will exist. All real materials contain defects. These defects, in terms of dimensionality, can be vacancies and interstitials which are point defects, dislocations which are line defects, and grain boundaries which are plane defects.

Point defects cause an increase of the configurational entropy contribution to the free energy at nonzero temperatures and will therefore always be present.

simply bonding to one another, the B-O distance is equal to a/2, whereas the A-O

The orthorhombic (**Figure 2**) and tetragonal (**Figure 3**) phases are the most common non-cubic variants [26] with octahedral distortions and translational A site offsets. As previously mentioned, green spheres represent A cations, blue spheres

Perovskites allow chemical tailoring because of the wide range of ions and valences which they can accommodate. By suitable formulation many valuable properties can be tailored. One interesting quality of perovskites is that they can accommodate more than one element for both A- and B sites constituting complex

tional aliovalent cations residing on the host cation sites generate oxygen vacancies. Furthermore for the B site, the element of transition metal can be in different oxidation states A(B'xB"y)O3, where x + y = 1. Aliovalent substitutions require a charge compensation mechanism because the ionic compound must be neutral. Therefore, either ion vacancies are created or one of the metals is partially or fully

Another interesting and useful to deal with is the complex set of phase relation-

The perovskite structure also lends itself to the building of superstructures as

A second family of superstructures are the Aurivillius phases (**Figure 5**) [29]. This is represented by the general formula (Bi2O2)(An1BnO3n+1), where A is a large monovalent, divalent, or trivalent 12-coordinate cation and B is a small trivalent, pentavalent, or hexavalent metallic 6-coordinate cation. Basically, their structure is

Various synthesis methods have been developed for the preparation of perovskite materials while managing efficiently the environmentally friendly processing in conjunction with phase structure tailored to the needed properties. Small changes in the crystal will have a large impact on functional properties, crystallinity, and stability. Among these techniques, dry ways like solid-state reaction mechanochemical processing or wet routes like sol–gel and microwave methods are

In crystalline state an array of atoms is regularly repeated in three dimensions. This construction leads to a perfect crystalline solid with all atoms present and located in their ideal positions. However, a zero entropy is needed for the perfect crystalline state to exist. Above absolute zero temperature is a probability that defects from ideality will exist. All real materials contain defects. These defects, in terms of dimensionality, can be vacancies and interstitials which are point defects, dislocations which are line defects, and grain boundaries which are

Point defects cause an increase of the configurational entropy contribution to the free energy at nonzero temperatures and will therefore always be present.

ships. These are useful in such materials because they are sensitive to external conditions, including temperature, pressure, strain, and composition [28].

seen in **Figure 4**. The Ruddlesden-Popper phases are a series of structures consisting of sequences of max 3 n; perovskite blocks are separated by a rock-salt structure block. The first member of the Ruddlesden-Popper series is A2BO4 or ABO3-AO which is isostructural with potassium tetrafluoridenickelate (II) K2NiF4,

1–xA2

x)BO3, A(B<sup>1</sup>

<sup>+</sup> and perovskite blocks (An–1BnO3n+1)2 that

1–xB<sup>2</sup>

x)O3. Substitu-

distance is equal to (a/√2) where a = length of unit cell.

perovskites. These can be represented as (A1

*Perovskite Materials, Devices and Integration*

reduced or oxidized.

the prototype structure.

widely used.

plane defects.

**100**

built by alternating layers of [Bi2O2]2

contain a layer of octahedral B sites.

**3. Perovskite defect chemistry**

represent B cations, and red spheres represent oxygen anions.

The formation of a point defect can be considered as a chemical reaction. At constant temperature, T, and pressure, p, the reaction is carried on in the direction that lowers the Gibbs free energy as follows:

$$\mathbf{G} = \mathbf{U} + \mathbf{p}\mathbf{V} - \mathbf{T}\mathbf{S} = \mathbf{H} - \mathbf{T}\mathbf{S} \tag{2}$$

where H is the enthalpy, U is the internal energy, S is the entropy, and V is the volume. The enthalpy H is defined as

$$\mathbf{H} = \mathbf{U} + \mathbf{p}\mathbf{V} \tag{3}$$

The change in free energy for the formation of n independent defects can be written as follows:

$$
\Delta \mathbf{G} = \mathbf{n} \Delta\_{\mathbf{f}} \mathbf{G} - \mathbf{T} \Delta\_{\mathbf{f}} \mathbf{S}\_{\mathbf{c}} \tag{4}
$$

In the above equation, the configurational entropy *Δ<sup>f</sup> Sc* is the part of the entropy change associated with randomly distributing n defect in the material. For a single defect, the formation free energy *ΔfG* is independent of the number of defects and can be written as follows:

$$
\Delta\_{\rm f} \mathbf{G} = \Delta\_{\rm f} \mathbf{U} + \mathbf{p} \Delta\_{\rm f} \mathbf{V} - \mathbf{T} \Delta\_{\rm f} \mathbf{S} \tag{5}
$$

The point defects are a nonstoichiometric perturbation of the ideal lattice having or not electrically charge. Materials can also be prepared in such a way as to increase the number of defects.

There are two main categories for point defects: intrinsic defects and extrinsic defects. The intrinsic defects are internal to the crystal. The extrinsic defects are created when an impurity atom or ion is inserted into the lattice. The main categories of intrinsic defects are Schottky disorder and Frenkel disorder.

The Schottky disordering mechanism presumes that atoms leave their sites in the crystal bulk and rebuild the crystal lattice on the surface. As a result, the vacancies are formed in both cation and anion sublattices. According to the Frenkel mechanism, an atom moves from its regular site to the nearest interstitial position; hence, two types of defect are formed in the crystal, namely, the vacancy and the interstitial atom.

A vacancy is formed if an atom is not present on the site that it should occupy in a perfect crystal. By removing one atom from the chemical formula of perovskite, a set of vacancies called Schottky defect is created, which is the removal of an oxygen atom. Oxygen ion has a charged of �2. The defect left behind after removal, a charge of +2, for an oxygen atom will be *VÖ* in Kröger-Vink notation. The following equation is written for the creation of oxygen vacancy, Schottky disorder:

$$\mathbf{O}\_{\rm O}^{X} = \frac{1}{2}\mathbf{O}\_{2} + \mathbf{V}\_{\rm O} + 2\mathbf{e}' \tag{6}$$

V indicates a vacancy, the subscript O indicates the oxygen host site, and superscript denoted by two dots is the defect charge of +2.

An interstitial is an ion situated on any site that would be unoccupied in a perfect crystal. The interstitial is denoted by a subscript *i*, in Kröger-Vink notation. Frenkel defects deal with the displacement of the ions from its sites to interstitial sites.

When an ion is substituted with an ion of different valence, another type of point defect is created, called substitutional defect.

Defect chemistry complies with the conservation rules which indicate the charge conservation by maintaining crystal electrical neutrality overall, and the mass balance and host structure should be preserved.

The possible point defects in ABO3 perovskite are the oxygen vacancies, A site vacancies, B vacancies, A interstitials, and B interstitials. The metal interstitial, B interstitial, defects are not energetically favored and less likely to be present.

Let us have a look at the LaCoO3 simultaneous doping on the A site and B site, with Sr., respectively, Fe and Cr. This is a way to increase oxide ion conductivity and at the same time to retain the required thermodynamic stability of doped lanthanum cobaltite.

Substitution of Cr3+ for Co3+ in the LaCoO3 results in the formation of Cr4+ according to the reaction

$$\mathbf{C}\mathbf{o}\_{\mathrm{Co}}^{\mathrm{X}} + \mathbf{C}\mathbf{r}\_{\mathrm{Co}}^{\mathrm{X}} = +\mathbf{C}\mathbf{o}\_{\mathrm{Co}}^{\prime} + \mathbf{C}\mathbf{r}\_{\mathrm{Co}}^{\bullet} \tag{7}$$

The charge may be transported by electrons or holes, by ions, or by both. There are also solids that exhibit simultaneously significant levels of both ionic and electronic transport and are referred to as mixed conductors, MIECs. While ionic conduction is mainly related to crystal structure, electronic conduction is deter-

The conductivity is proportional to the concentration of charge carriers noted ci carriers/Volume; the charge they carry is zie (C/charge), where e is the unit electronic charge, mobility noted μi, which is their ability to move in an electric field. Having zi unit charges on the carrier is described for their mobility to move in an

σ<sup>i</sup> ¼ cizieμ<sup>i</sup> (11)

dx (12)

.

electric field by their mobility μi; the conductivity is described by the relations

where ci is the concentration of charge carriers per volume and zie the charge

In response to a concentration gradient, the system attempts to return to a homogenous equilibrium state by eliminating the gradient. The Fick's first law

Ji ¼ Di

*dx* is the concentration gradient of species i, Ji is its flux in

A solid oxide fuel cell, SOFC, essentially consists of two porous electrodes separated by a dense, oxide ion-conducting electrolyte. The operating principle of such a cell is illustrated in **Figure 6**. The oxygen supplied at the cathode or, air electrode, reacts with incoming electrons from the external circuit to form oxide ions, which migrate to the anode or, fuel electrode, through the oxide ion

conducting electrolyte. At the anode side, the oxide ions combine with H2, CO in the fuel to form H2O, CO2, with the effect of liberating electrons. Electrons flow from the anode through the external circuit to the cathode. To keep the cell resis-

Due to its operating conditions there are some limitations to materials used for

These materials should be durable without changes of the required properties. Until now, there have been several researches to develop and fabricate materials to

Electrolyte may carry either oxide ion O2� or proton H<sup>+</sup> and should have high ionic conductivity and uniform features in structure. The important properties of cathodes are high electronic conductivity and thin porous layer where the oxygen reduction reaction takes place. The anode materials must be chemically compatible with electrolyte. Thermal expansion also is a requirement to match with electrolyte thermal expansion characteristics. The thermal expansion of solids depends on their structure symmetry and may be either isotropic or anisotropic. Properties like electrical conductivity, large triple phase boundary, and high electrocatalytic

meet requirements of SOFC. **Table 1** summarizes such perovskite materials

tance low, the electrolyte is fabricated in the form of a thin film.

, and Di is the diffusion constant in particles\*cm�<sup>4</sup>

dci�

mined by the electronic bandgap.

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

they carry in C per charge.

where *dci*

particles\*cm�<sup>2</sup>

SOFC.

**103**

*=*

\*s�<sup>1</sup>

**5. Clean energy applications**

**5.1 Perovskites in solid oxide fuel cell**

accordingly to the SOFC component.

describes the unidirectional diffusion:

The charge disproportionation equation for Co site is

$$\mathbf{2Co}\_{\text{Co}}^{\text{X}} = \mathbf{Co}\_{\text{Co}}^{\bullet} + \mathbf{Co}\_{\text{Co}}^{\prime} \tag{8}$$

Using Kröger-Vink notations *CoX Co*, *Co*<sup>∙</sup> *Co*, Cr4+, *Co*<sup>0</sup> *Co*, *CrX Co*, and *Cr*<sup>∙</sup> *Co* indicates Cr3+, Co4+, Co2+, and Cr3+, respectively.

For the ions of Fe3+ doping on the Co3+ site, is a similar behavior. Their interaction is leading to form Fe2+, Fe4+ and Co2+, Co4+, respectively.

Sr2+ on La3+ sites is represented by the negatively effective charged *Sr*<sup>0</sup> *La*.

Within the framework of standard band approach, thermally activated electrons can jump from the valence band via the bandgap toward the conduction band. For conduction band electrons e and valence band holes h, the relevant equation is

$$\mathbf{h} \mathbf{n} \mathbf{l} = \mathbf{e}' + \mathbf{h}^\* \tag{9}$$

A free electron in the conduction band and an itinerant hole in the valence band appear simultaneously.

Owing to its intrinsic zero-dimensional nature, a point defect, or any single atom, is difficult to observe experimentally, and much of the knowledge about point defects is inferred by implicit methods.

## **4. Perovskites transport properties**

The key important factors for the ionic transport of perovskite materials are their defect chemistry and crystal structure. Point defects, mainly ionic defects, have major impact on transport properties like ionic diffusion and ionic conductivity. These properties are the most important in technical applications mentioned in this chapter, dealing with movement of ions within crystal.

Vacancies, interstitials, and substitutional defects can all be charged. The linear response that relates the current density to the applied field is the conductivity. This proportionality constant can be expressed as follows:

$$\mathbf{I}\_{\mathbf{i}} = \sigma\_{\mathbf{i}} \mathbf{E} \tag{10}$$

where E is the applied electric field in V\*cm�<sup>1</sup> , Ii is the current density for species i in A\*cm�<sup>2</sup> , and σ<sup>i</sup> is the conductivity σ<sup>i</sup> in 1\*Ω�<sup>1</sup> \*cm�<sup>1</sup> .

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

Defect chemistry complies with the conservation rules which indicate the charge

vacancies, A site vacancies, B vacancies, A interstitials, and B interstitials. The metal interstitial, B interstitial, defects are not energetically favored and less likely to

Let us have a look at the LaCoO3 simultaneous doping on the A site and B site, with Sr., respectively, Fe and Cr. This is a way to increase oxide ion conductivity and at the same time to retain the required thermodynamic stability of doped

Substitution of Cr3+ for Co3+ in the LaCoO3 results in the formation of Cr4+

Co ¼ þCo<sup>0</sup>

For the ions of Fe3+ doping on the Co3+ site, is a similar behavior. Their interac-

Within the framework of standard band approach, thermally activated electrons can jump from the valence band via the bandgap toward the conduction band. For conduction band electrons e and valence band holes h, the relevant equation is

A free electron in the conduction band and an itinerant hole in the valence band

Owing to its intrinsic zero-dimensional nature, a point defect, or any single atom, is difficult to observe experimentally, and much of the knowledge about

The key important factors for the ionic transport of perovskite materials are their defect chemistry and crystal structure. Point defects, mainly ionic defects, have major impact on transport properties like ionic diffusion and ionic conductivity. These properties are the most important in technical applications mentioned in

Vacancies, interstitials, and substitutional defects can all be charged. The linear response that relates the current density to the applied field is the conductivity. This

, and σ<sup>i</sup> is the conductivity σ<sup>i</sup> in 1\*Ω�<sup>1</sup>

Co <sup>¼</sup> Co<sup>∙</sup>

*Co*, *Co*<sup>∙</sup>

Sr2+ on La3+ sites is represented by the negatively effective charged *Sr*<sup>0</sup>

Co <sup>þ</sup> Cr<sup>∙</sup>

*Co*, *CrX*

nil <sup>¼</sup> <sup>e</sup><sup>0</sup> <sup>þ</sup> <sup>h</sup><sup>∙</sup> (9)

Ii ¼ σiE (10)

\*cm�<sup>1</sup> .

, Ii is the current density for

Co þ Co<sup>0</sup>

*Co*, Cr4+, *Co*<sup>0</sup>

Co (7)

Co (8)

*Co* indicates

*La*.

*Co*, and *Cr*<sup>∙</sup>

conservation by maintaining crystal electrical neutrality overall, and the mass

The possible point defects in ABO3 perovskite are the oxygen

CoX

The charge disproportionation equation for Co site is

tion is leading to form Fe2+, Fe4+ and Co2+, Co4+, respectively.

Co <sup>þ</sup> Cr<sup>X</sup>

2CoX

balance and host structure should be preserved.

*Perovskite Materials, Devices and Integration*

be present.

lanthanum cobaltite.

according to the reaction

appear simultaneously.

species i in A\*cm�<sup>2</sup>

**102**

Using Kröger-Vink notations *CoX*

Cr3+, Co4+, Co2+, and Cr3+, respectively.

point defects is inferred by implicit methods.

this chapter, dealing with movement of ions within crystal.

proportionality constant can be expressed as follows:

where E is the applied electric field in V\*cm�<sup>1</sup>

**4. Perovskites transport properties**

The charge may be transported by electrons or holes, by ions, or by both. There are also solids that exhibit simultaneously significant levels of both ionic and electronic transport and are referred to as mixed conductors, MIECs. While ionic conduction is mainly related to crystal structure, electronic conduction is determined by the electronic bandgap.

The conductivity is proportional to the concentration of charge carriers noted ci carriers/Volume; the charge they carry is zie (C/charge), where e is the unit electronic charge, mobility noted μi, which is their ability to move in an electric field.

Having zi unit charges on the carrier is described for their mobility to move in an electric field by their mobility μi; the conductivity is described by the relations

$$
\sigma\_{\mathbf{i}} = \mathbf{c}\_{\mathbf{i}} \mathbf{z}\_{\mathbf{i}} \mathbf{e} \mu\_{\mathbf{i}} \tag{11}
$$

where ci is the concentration of charge carriers per volume and zie the charge they carry in C per charge.

In response to a concentration gradient, the system attempts to return to a homogenous equilibrium state by eliminating the gradient. The Fick's first law describes the unidirectional diffusion:

$$\mathbf{J}\_{\mathrm{i}} = \mathbf{D}\_{\mathrm{i}} \frac{\mathbf{dc}\_{\mathrm{i}-}}{\mathbf{dx}} \tag{12}$$

where *dci=dx* is the concentration gradient of species i, Ji is its flux in particles\*cm�<sup>2</sup> \*s�<sup>1</sup> , and Di is the diffusion constant in particles\*cm�<sup>4</sup> .

## **5. Clean energy applications**

### **5.1 Perovskites in solid oxide fuel cell**

A solid oxide fuel cell, SOFC, essentially consists of two porous electrodes separated by a dense, oxide ion-conducting electrolyte. The operating principle of such a cell is illustrated in **Figure 6**. The oxygen supplied at the cathode or, air electrode, reacts with incoming electrons from the external circuit to form oxide ions, which migrate to the anode or, fuel electrode, through the oxide ion conducting electrolyte. At the anode side, the oxide ions combine with H2, CO in the fuel to form H2O, CO2, with the effect of liberating electrons. Electrons flow from the anode through the external circuit to the cathode. To keep the cell resistance low, the electrolyte is fabricated in the form of a thin film.

Due to its operating conditions there are some limitations to materials used for SOFC.

These materials should be durable without changes of the required properties. Until now, there have been several researches to develop and fabricate materials to meet requirements of SOFC. **Table 1** summarizes such perovskite materials accordingly to the SOFC component.

Electrolyte may carry either oxide ion O2� or proton H<sup>+</sup> and should have high ionic conductivity and uniform features in structure. The important properties of cathodes are high electronic conductivity and thin porous layer where the oxygen reduction reaction takes place. The anode materials must be chemically compatible with electrolyte. Thermal expansion also is a requirement to match with electrolyte thermal expansion characteristics. The thermal expansion of solids depends on their structure symmetry and may be either isotropic or anisotropic. Properties like electrical conductivity, large triple phase boundary, and high electrocatalytic

(La, Sr)(Co, Fe)O3 about 330 S/cm [41], and (La, Sr)CoO3 about 1.22–1.60 S/cm [42, 43]. (Pr, Ba, Sr)(Co, Fe)O5 is a promising cathode material with power densities about 2.2 W/cm<sup>2</sup> at 600°C and has potential for commercially viable SOFC technologies [44]. The choice of material combinations for the SOFC components is

Transition metal perovskites are important catalyst materials. The catalytic activity for perovskite materials often resides with metal oxide surface sites, and efficient use of the metals and space available requires small particles, located on a mostly inert support to enhance the thermal stability of the catalyst. Direct electrochemical water splitting is considered a key process in the development of novel energy storage systems, crucial for a sustainable and environmentally friendly energy economy. Water electrolyzers can convert water into hydrogen and oxygen through an electrochemical process, allowing H2 to be stored as an energy vector

However, the overpotentials at the anode side where the oxygen evolution reaction, OER, takes place are substantial, even when highly active, precious metal catalysts are used. Therefore, the development of anode materials based on inexpensive and abundant elements, displaying both high OER activity and stability, appears to be a crucial point toward the development of new-generation hydrogenbased storage systems. The values of OER activity about four times higher than that of bulk LaCoO3 compound which was found to be 1.87 A/g were reported for porous and nanosphere LaCoO3. For porous LaCoO3, an OER activity of 7.51 A/g was reported, and for hollow LaCoO3 nanospheres, an OER activity of 12.58 A/g was

The oxygen evolution reaction OER in alkaline has the net reaction:

Typically in electrocatalysis the ion of interest is the B site assumed to be an active site for OER. From a crystal field theory perspective, the octahedrally coordinated B site state d will split into several levels. The states of interest for catalysis will be the antibonding eg and t2g states since they are typically the occupied states with highest energy and their filling will roughly determine the strength of the

*Working principle of an alkaline electrolysis cell. When the direct current is applied to the water, oxygen and hydrogen are separated from the water. Oxygen arises at the anode while the hydrogen at the cathode.*

4HO� ¼ 2H2O þ O2 þ 4e� (13)

crucial for determining their performances.

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

reported. Both values are at 1.60 V [45].

**5.2 Perovskites in catalysis**

as is seen in **Figure 7**.

B-O bond.

**Figure 7.**

**105**

#### **Figure 6.**

*Operating principle of a solid oxide fuel cell. (a) Operating principle of a solid oxide fuel cell: Oxygen ionconducting type cell. (b) Operating principle of a solid oxide fuel cell: Hydrogen ion-conducting type cell.*


### **Table 1.**

*Typical materials used in solid oxide fuel cells.*

activity provide a mechanism for electronic conductivity, constituting important qualities to take in account from anode materials. Among the materials developed for SOFC components, (La, Sr)MnO3 in air shows a conductivity of 300 S/cm [40], (La, Sr)(Co, Fe)O3 about 330 S/cm [41], and (La, Sr)CoO3 about 1.22–1.60 S/cm [42, 43]. (Pr, Ba, Sr)(Co, Fe)O5 is a promising cathode material with power densities about 2.2 W/cm<sup>2</sup> at 600°C and has potential for commercially viable SOFC technologies [44]. The choice of material combinations for the SOFC components is crucial for determining their performances.

## **5.2 Perovskites in catalysis**

Transition metal perovskites are important catalyst materials. The catalytic activity for perovskite materials often resides with metal oxide surface sites, and efficient use of the metals and space available requires small particles, located on a mostly inert support to enhance the thermal stability of the catalyst. Direct electrochemical water splitting is considered a key process in the development of novel energy storage systems, crucial for a sustainable and environmentally friendly energy economy. Water electrolyzers can convert water into hydrogen and oxygen through an electrochemical process, allowing H2 to be stored as an energy vector as is seen in **Figure 7**.

However, the overpotentials at the anode side where the oxygen evolution reaction, OER, takes place are substantial, even when highly active, precious metal catalysts are used. Therefore, the development of anode materials based on inexpensive and abundant elements, displaying both high OER activity and stability, appears to be a crucial point toward the development of new-generation hydrogenbased storage systems. The values of OER activity about four times higher than that of bulk LaCoO3 compound which was found to be 1.87 A/g were reported for porous and nanosphere LaCoO3. For porous LaCoO3, an OER activity of 7.51 A/g was reported, and for hollow LaCoO3 nanospheres, an OER activity of 12.58 A/g was reported. Both values are at 1.60 V [45].

The oxygen evolution reaction OER in alkaline has the net reaction:

$$\text{4HO}^- = \text{2H}\_2\text{O} + \text{O}\_2 + 4\text{e}^- \tag{13}$$

Typically in electrocatalysis the ion of interest is the B site assumed to be an active site for OER. From a crystal field theory perspective, the octahedrally coordinated B site state d will split into several levels. The states of interest for catalysis will be the antibonding eg and t2g states since they are typically the occupied states with highest energy and their filling will roughly determine the strength of the B-O bond.

**Figure 7.**

*Working principle of an alkaline electrolysis cell. When the direct current is applied to the water, oxygen and hydrogen are separated from the water. Oxygen arises at the anode while the hydrogen at the cathode.*

activity provide a mechanism for electronic conductivity, constituting important qualities to take in account from anode materials. Among the materials developed for SOFC components, (La, Sr)MnO3 in air shows a conductivity of 300 S/cm [40],

Electrolyte LaGaO3-type [30]: (La,Sr)(Ga,Mg)O3, (La,Sr)(Ga,MgCo)O3, (La,Sr)(Ga,Mg,Fe)

*Operating principle of a solid oxide fuel cell. (a) Operating principle of a solid oxide fuel cell: Oxygen ionconducting type cell. (b) Operating principle of a solid oxide fuel cell: Hydrogen ion-conducting type cell.*

O3, (La,Sr)(Ga,Mg,Co,Fe)O3

Cathode LaMnO3-type [33]: (La,Sr)MnO3, (La,Ca)MnO3

(Sm,Sr)CoO3, (Sm,Nd)CoO3,

Separator LaCrO3 type [38, 39]: (La,Sr)CrO3, (La,Ca)CrO3

(La,Sr)FeO3 [35]

LaNiO3 K2NiF4 structure

Anode SrNbO3 [36]; SrVO3 [37]

*Typical materials used in solid oxide fuel cells.*

LaAlO3-type [31]: (La,Ca)AlO3, (La,Ba)AlO3 Brownmillerite perovskite: BaZrO3 [32]

LaCoO3-type [34]: (La,Sr)CoO3, (La,Ca)CoO3

**Component part Material**

*Perovskite Materials, Devices and Integration*

**Table 1.**

**104**

**Figure 6.**

The OER activities of a series of perovskites were found to form a volcano trend when plotted versus the eg orbital filling determined using X-ray absorption nearedge structure (XANES) and spin states inferred [46]. Perovskites with an eg orbital occupancy of approximately 1 were found to be the most active. Based on this principle, highly active perovskite catalysts like Ba0.5Sr0.5Co0.8Fe0.2O3 with a conductivity of 8.58 <sup>10</sup><sup>5</sup> S/cm, LaNiO3 which has 2.39 S/cm, and LaCoO3 can be used to rationally choose materials as candidates for promising OER catalyst [45, 47–52].

through compositional variations; perovskites show promise for solar hydrogen production among the large number of photocatalysts being explored. As example of photocatalysts can be mentioned perovskites with formula AFeO3, where A: La, Pr, Ce, and perovskites with formula LaBO3 where B: Co, Mn, Fe [53–55]. Under visible light LaFeO3 with a bandgap of 2.1 eV has an oxygen evolution rate of 331.5 μmol/h\*g in ethanol [56]; SrTiO3 with a bandgap of 3.2 eV has a rate of 18.8 μmol/h\*g in ethanol [57]. Perovskite materials are also frequently explored in combination with other oxides to carry out various steps of complex uphill reactions involved in water splitting reactions. In **Figure 8**, the schematic of the reaction processes involved in overall water splitting is shown. When the energy of incident light is larger than that of a bandgap, electrons and holes are generated in the

The perovskites tailored through bandgap engineering approaches can harvest solar light more effectively. Such perovskites show broadband absorption over the visible to near-infrared region of the solar spectrum. Another challenge related to the charge separation between photogenerated holes and electrons has also been undertaken with perovskite compositions to achieve overall improved efficiency.

In the last years environment-friendly and clean energy have attracted worldwide attention due to the growing concerns about global warming and other environmental issues associated with the heavy consumption of fossil fuels. Currently, new functional materials and adaptations to existing functional materials and their use are undergoing extensive investigation and have seen a remarkable development. Perovskites drive interest in their research investigations because the promise of their excellent features to be used in important technological devices such as the

We described the observed remarkable feature of adjustable structure properties

functional performances. The perovskite structure is viable to wide departures in compositions from the ideal formula ABO3. The presence of defects can change the properties of the material. When these are properly controlled, defects are the material engineer's way of tuning material properties into wanted effects.

For real world applications, there are still some challenges to tackle in order to achieve the primary goal of the energy field when perovskites with different morphologies are the target materials. Oxide perovskite materials are a competitive alternative to low-cost non-noble metal-based functional materials with high activity and stability to replace the state-of-the-art material. Approaches to prepare perovskites are usually complicated and need harsh reaction conditions like high temperatures, in most of the cases. The large-scale synthesis of perovskites is also a great challenge to researchers since most work is still limited to laboratory scale. Therefore, searching for new facile and environmentally friendly approach to syn-

It can be seen from the above discussion that there are many positive outcomes in the continuous development of perovskite materials rationally engineered by defect chemistry and controlled morphologies through the preparation methods. Great efforts are dedicated for the use of *in-situ* characterization techniques like X-ray diffraction or microscopy, so we can explain how structural modifications, alterations in the morphology, degradation speed of perovskite happened. Moving toward commercialization it is necessary to ensure low cost and long-term stability

for perovskites, leaving room for obtaining perovskite oxides with better

conduction and valence bands, respectively.

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

solid oxide fuel cell, water electrolysis, and photocatalysts.

thesize perovskites is still of great importance in this field.

of materials which represent a significant active research direction.

**107**

**6. Conclusions and outlook**

## **5.3 Perovskites in photocatalysis**

In general, an efficient photocatalyst, also called an ideal semiconductor, should include light-harvesting and redox capabilities to facilitate the desired chemical reactions, thus achieving the targeted reaction. Inorganic semiconductor materials should have adequate capability to absorb solar energy across a broad spectrum. Because of their light-harvesting property, potential photocatalysts absorb solar energy, leading to the generation of photoelectrons in the conduction band and holes in the valence band for their possible use in redox reactions.

The redox nature of a photocatalyst as an intrinsic property dictates solar energy conversion efficiency. Most semiconductors include metals/mixed metal oxides used as efficient photocatalysts with the exceptional adaptability of their properties

**Figure 8.**

*Schematic of the reaction processes involved in overall water splitting. (a) The processes of photocatalytic water splitting. (b) Water molecules are oxidized by the holes to form O2 and reduced by the electrons to form H2.*

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

The OER activities of a series of perovskites were found to form a volcano trend when plotted versus the eg orbital filling determined using X-ray absorption nearedge structure (XANES) and spin states inferred [46]. Perovskites with an eg orbital occupancy of approximately 1 were found to be the most active. Based on this principle, highly active perovskite catalysts like Ba0.5Sr0.5Co0.8Fe0.2O3 with a conductivity of 8.58 <sup>10</sup><sup>5</sup> S/cm, LaNiO3 which has 2.39 S/cm, and LaCoO3 can be used to rationally choose materials as candidates for promising OER catalyst [45, 47–52].

In general, an efficient photocatalyst, also called an ideal semiconductor, should include light-harvesting and redox capabilities to facilitate the desired chemical reactions, thus achieving the targeted reaction. Inorganic semiconductor materials should have adequate capability to absorb solar energy across a broad spectrum. Because of their light-harvesting property, potential photocatalysts absorb solar energy, leading to the generation of photoelectrons in the conduction band and

The redox nature of a photocatalyst as an intrinsic property dictates solar energy conversion efficiency. Most semiconductors include metals/mixed metal oxides used as efficient photocatalysts with the exceptional adaptability of their properties

*Schematic of the reaction processes involved in overall water splitting. (a) The processes of photocatalytic water splitting. (b) Water molecules are oxidized by the holes to form O2 and reduced by the electrons to form H2.*

holes in the valence band for their possible use in redox reactions.

**5.3 Perovskites in photocatalysis**

*Perovskite Materials, Devices and Integration*

**Figure 8.**

**106**

through compositional variations; perovskites show promise for solar hydrogen production among the large number of photocatalysts being explored. As example of photocatalysts can be mentioned perovskites with formula AFeO3, where A: La, Pr, Ce, and perovskites with formula LaBO3 where B: Co, Mn, Fe [53–55]. Under visible light LaFeO3 with a bandgap of 2.1 eV has an oxygen evolution rate of 331.5 μmol/h\*g in ethanol [56]; SrTiO3 with a bandgap of 3.2 eV has a rate of 18.8 μmol/h\*g in ethanol [57]. Perovskite materials are also frequently explored in combination with other oxides to carry out various steps of complex uphill reactions involved in water splitting reactions. In **Figure 8**, the schematic of the reaction processes involved in overall water splitting is shown. When the energy of incident light is larger than that of a bandgap, electrons and holes are generated in the conduction and valence bands, respectively.

The perovskites tailored through bandgap engineering approaches can harvest solar light more effectively. Such perovskites show broadband absorption over the visible to near-infrared region of the solar spectrum. Another challenge related to the charge separation between photogenerated holes and electrons has also been undertaken with perovskite compositions to achieve overall improved efficiency.

## **6. Conclusions and outlook**

In the last years environment-friendly and clean energy have attracted worldwide attention due to the growing concerns about global warming and other environmental issues associated with the heavy consumption of fossil fuels. Currently, new functional materials and adaptations to existing functional materials and their use are undergoing extensive investigation and have seen a remarkable development. Perovskites drive interest in their research investigations because the promise of their excellent features to be used in important technological devices such as the solid oxide fuel cell, water electrolysis, and photocatalysts.

We described the observed remarkable feature of adjustable structure properties for perovskites, leaving room for obtaining perovskite oxides with better functional performances. The perovskite structure is viable to wide departures in compositions from the ideal formula ABO3. The presence of defects can change the properties of the material. When these are properly controlled, defects are the material engineer's way of tuning material properties into wanted effects.

For real world applications, there are still some challenges to tackle in order to achieve the primary goal of the energy field when perovskites with different morphologies are the target materials. Oxide perovskite materials are a competitive alternative to low-cost non-noble metal-based functional materials with high activity and stability to replace the state-of-the-art material. Approaches to prepare perovskites are usually complicated and need harsh reaction conditions like high temperatures, in most of the cases. The large-scale synthesis of perovskites is also a great challenge to researchers since most work is still limited to laboratory scale. Therefore, searching for new facile and environmentally friendly approach to synthesize perovskites is still of great importance in this field.

It can be seen from the above discussion that there are many positive outcomes in the continuous development of perovskite materials rationally engineered by defect chemistry and controlled morphologies through the preparation methods. Great efforts are dedicated for the use of *in-situ* characterization techniques like X-ray diffraction or microscopy, so we can explain how structural modifications, alterations in the morphology, degradation speed of perovskite happened. Moving toward commercialization it is necessary to ensure low cost and long-term stability of materials which represent a significant active research direction.

## **Acknowledgements**

This work was supported by the National Authority for Scientific Research and Innovation/Romanian Ministry of Education and Research, project "RESTORE"—117/16.09.2016 ID/Cod My SMIS: P\_37\_595 / 104958.

## **Conflict of interest**

The authors state that there is no conflict of interest associated with this work.

**References**

BF01303701

04.069

[1] Thurnaurer H, Deaderick J. U.S. Patent No. 2,429,588 filed (1941); 1947

T superconductivity in the

[2] Bednorz JG, Müller KA. Possible high

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

perovskite bismuth oxide prepared by a

International. 2014;**53**(14):3599-3603. DOI: 10.1002/ANIE.201400607

low-temperature hydrothermal reaction. Angewandte Chemie

[9] Kim DC, Baranov AN, Kim JS, Kang HR, Kim BJ, Kim YC, et al. High pressure synthesis and superconductivity of Ba1xKxBiO3 (0.35<x<1). Physica C: Superconductivity. 2003;**383**(4):343-353. DOI: 10.1016/S0921-4534(02)01332-1

[10] Phraewphiphat T, Iqbal M, Suzuki K, Matsuda Y, Yonemura M, Hirayama M, et al. Syntheses, structures, and ionic conductivities of perovskite-structured lithium– strontium–aluminum/gallium–

10.1016/j.jssc.2015.01.007

j.ssi.2018.06.014

2018.03.156

tantalum-oxides. Journal of Solid State Chemistry. 2015;**225**:431-437. DOI:

[11] Salles C, Bassat JM, Fouletier J, Marinha D, Steil M-C. Oxygen pressure dependence of the ionic conductivity of iron-doped calcium titanate. Solid State Ionics. 2018;**324**:103-108. DOI: 10.1016/

[12] Lin Q, Yang X, Lin J, Guo Z, He Y. The structure and magnetic properties of magnesium-substituted LaFeO3 perovskite negative electrode material by citrate sol-gel. International Journal of Hydrogen Energy. 2018;**43**(28): 12720-12729. DOI: 10.1016/j.ijhydene.

[13] Goswami S, Bhattacharya D. Magnetic transition at 150 K in nanoscale BiFeO3. Journal of Alloys and Compounds. 2018;**738**:277-282. DOI: 10.1016/j.jallcom.2017.12.107

[14] Zhang F, Zhang X, Jiang G, Li N, Hao Z, Qu S. H2S selective catalytic oxidation over Ce substituted. Chemical Engineering Journal. 2018;**348**:831-839.

DOI: 10.1016/j.cej.2018.05.050

BaLaCuO system. Zeitschrift fur Physik B: Condensed Matter. 1986; **64**(2):189-193. DOI: 10.1007/

[3] Tonui P, Oseni SO, Sharma G, Yan Q, Mola GT. Perovskites

current status. Renewable and Sustainable Energy Reviews. 2018;**91**: 1025-1044. DOI: 10.1016/j.rser.2018.

[4] Alvarez G, Conde-Gallardo A, Montiel H, Zamorano R. About room temperature ferromagnetic behavior in

[5] Zheng T, Wu J, Xiao D, Zhu J. Recent development in lead-free perovskite piezoelectric bulk materials. Progress in Materials Science. 2018;**98**:552-624. DOI: 10.1016/j.pmatsci.2018.06.002

conductivity of (Mg,Fe)SiO3 perovskite and a perovskite-dominated assemblage at lower. Geophysical Research Letters. 1987;**14**(11):1075-1078. DOI: 10.1029/

BaTiO3 perovskite. Journal of Magnetism and Magnetic Materials. 2016;**401**:196-199. DOI: 10.1016/j.

[6] Li X, Jeanloz R. Electrical

[7] Presto S, Kumar P, Varma S, Viviani M, Singh P. Electrical conductivity of NiMo-based double perovskites under SOFC anodic conditions. International Journal of Hydrogen Energy. 2018;**43**(9): 4528-4533. DOI: 10.1016/j. ijhydene.2018.01.066

[8] Rubel MHK, Miura A, Takei T, Kumada N, Mozahar Ali N, Nagao M,

et al. Superconducting double

**109**

jmmm.2015.10.031

GL014i011p01075

photovoltaic solar cells: An overview of

## **Author details**

Mirela Dragan<sup>1</sup> \*, Stanica Enache<sup>1</sup> , Mihai Varlam<sup>1</sup> and Konstantin Petrov<sup>2</sup>

1 National R&D Institute for Cryogenic and Isotope Technologies, Ramnicu Valcea, Romania

2 Academician Evgeni Budevski Institute of Electrochemistry and Energy Systems, Sofia, Bulgaria

\*Address all correspondence to: mirela.dragan@icsi.ro

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

## **References**

**Acknowledgements**

*Perovskite Materials, Devices and Integration*

**Conflict of interest**

**Author details**

Mirela Dragan<sup>1</sup>

Sofia, Bulgaria

Romania

**108**

\*, Stanica Enache<sup>1</sup>

\*Address all correspondence to: mirela.dragan@icsi.ro

provided the original work is properly cited.

This work was supported by the National Authority for Scientific Research

The authors state that there is no conflict of interest associated with this work.

, Mihai Varlam<sup>1</sup> and Konstantin Petrov<sup>2</sup>

1 National R&D Institute for Cryogenic and Isotope Technologies, Ramnicu Valcea,

2 Academician Evgeni Budevski Institute of Electrochemistry and Energy Systems,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

and Innovation/Romanian Ministry of Education and Research, project "RESTORE"—117/16.09.2016 ID/Cod My SMIS: P\_37\_595 / 104958.

[1] Thurnaurer H, Deaderick J. U.S. Patent No. 2,429,588 filed (1941); 1947

[2] Bednorz JG, Müller KA. Possible high T superconductivity in the BaLaCuO system. Zeitschrift fur Physik B: Condensed Matter. 1986; **64**(2):189-193. DOI: 10.1007/ BF01303701

[3] Tonui P, Oseni SO, Sharma G, Yan Q, Mola GT. Perovskites photovoltaic solar cells: An overview of current status. Renewable and Sustainable Energy Reviews. 2018;**91**: 1025-1044. DOI: 10.1016/j.rser.2018. 04.069

[4] Alvarez G, Conde-Gallardo A, Montiel H, Zamorano R. About room temperature ferromagnetic behavior in BaTiO3 perovskite. Journal of Magnetism and Magnetic Materials. 2016;**401**:196-199. DOI: 10.1016/j. jmmm.2015.10.031

[5] Zheng T, Wu J, Xiao D, Zhu J. Recent development in lead-free perovskite piezoelectric bulk materials. Progress in Materials Science. 2018;**98**:552-624. DOI: 10.1016/j.pmatsci.2018.06.002

[6] Li X, Jeanloz R. Electrical conductivity of (Mg,Fe)SiO3 perovskite and a perovskite-dominated assemblage at lower. Geophysical Research Letters. 1987;**14**(11):1075-1078. DOI: 10.1029/ GL014i011p01075

[7] Presto S, Kumar P, Varma S, Viviani M, Singh P. Electrical conductivity of NiMo-based double perovskites under SOFC anodic conditions. International Journal of Hydrogen Energy. 2018;**43**(9): 4528-4533. DOI: 10.1016/j. ijhydene.2018.01.066

[8] Rubel MHK, Miura A, Takei T, Kumada N, Mozahar Ali N, Nagao M, et al. Superconducting double

perovskite bismuth oxide prepared by a low-temperature hydrothermal reaction. Angewandte Chemie International. 2014;**53**(14):3599-3603. DOI: 10.1002/ANIE.201400607

[9] Kim DC, Baranov AN, Kim JS, Kang HR, Kim BJ, Kim YC, et al. High pressure synthesis and superconductivity of Ba1xKxBiO3 (0.35<x<1). Physica C: Superconductivity. 2003;**383**(4):343-353. DOI: 10.1016/S0921-4534(02)01332-1

[10] Phraewphiphat T, Iqbal M, Suzuki K, Matsuda Y, Yonemura M, Hirayama M, et al. Syntheses, structures, and ionic conductivities of perovskite-structured lithium– strontium–aluminum/gallium– tantalum-oxides. Journal of Solid State Chemistry. 2015;**225**:431-437. DOI: 10.1016/j.jssc.2015.01.007

[11] Salles C, Bassat JM, Fouletier J, Marinha D, Steil M-C. Oxygen pressure dependence of the ionic conductivity of iron-doped calcium titanate. Solid State Ionics. 2018;**324**:103-108. DOI: 10.1016/ j.ssi.2018.06.014

[12] Lin Q, Yang X, Lin J, Guo Z, He Y. The structure and magnetic properties of magnesium-substituted LaFeO3 perovskite negative electrode material by citrate sol-gel. International Journal of Hydrogen Energy. 2018;**43**(28): 12720-12729. DOI: 10.1016/j.ijhydene. 2018.03.156

[13] Goswami S, Bhattacharya D. Magnetic transition at 150 K in nanoscale BiFeO3. Journal of Alloys and Compounds. 2018;**738**:277-282. DOI: 10.1016/j.jallcom.2017.12.107

[14] Zhang F, Zhang X, Jiang G, Li N, Hao Z, Qu S. H2S selective catalytic oxidation over Ce substituted. Chemical Engineering Journal. 2018;**348**:831-839. DOI: 10.1016/j.cej.2018.05.050

[15] Wang WL, Meng Q, Xue Y, Weng X, Sun P, Wu Z. Lanthanide perovskite catalysts for oxidation of chloroaromatics: Secondary pollution and modifications. Journal of Catalysis. 2018;**366**:213-222. DOI: 10.1016/j. jcat.2018.07.022

[16] Fang M, Yao X, Li W, Li Y, Shui M, Shu J. The investigation of lithium doping perovskite oxide LiMnO3 as possible LIB anode material. Ceramics International. 2018;**44**(7):8223-8231. DOI: 10.1016/j.ceramint.2018.02.002

[17] Yao C, Zhang H, Liu X, Meng J, Zhang X, Meng F, et al. Characterization of layered double perovskite LaBa0.5Sr0.25Ca0.25Co2O5+<sup>δ</sup> as cathode material for intermediate-temperature solid oxide fuel cells. Journal of Solid State Chemistry. 2018;**265**:72-78. DOI: 10.1016/j.jssc.2018.05.028

[18] Parganiha Y, Kaur J, Dubey V, Shrivastavac R. YAlO3:Ce3+ powders: Synthesis, characterization, thermoluminescence and optical studies. Superlattices and Microstructures. 2015;**85**:410-417. DOI: 10.1016/j.spmi.2015.06.011

[19] Baig HN, Saluja JK, Haranath D. Investigation of luminescence properties of Dy3+ doped YAlO3 phosphors synthesized through solid state method. Optik. 2016;**127**(20): 9178-9195. DOI: 10.1016/j. ijleo.2015.12.159

[20] Zhang Y, Tso CY, Iñigo JS, Liu S, Miyazaki H, Chao CYH, et al. Perovskite thermochromic smart window: Advanced optical properties and low transition temperature. Applied Energy. 2019;**254**:113690. DOI: 10.1016/j. apenergy.2019.113690

[21] Matsouka C, Zaspalis V, Nalbandian L. Perovskites as oxygen carriers in chemical looping reforming process—Preparation of dense perovskite membranes and ionic

conductivity measurement. Materials Today: Proceedings. 2018;**5**(14): 27543-27552. DOI: 10.1016/j. matpr.2018.09.074

[29] Knyazev AV, Mączka M, Krasheninnikova OV, Ptak M, Syrov EV, Trzebiatowska-Gussowska M. High-temperature X-ray diffraction and spectroscopic studies of some Aurivillius phases. Materials Chemistry and Physics. 2018;**204**:8-17. DOI: 10.1016/j.matchemphys.2017.10.022

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

> [35] Lakshminarayanan N, Kuhn JN, Rykov SA, Millet JMM, Ozkan US. Doped LaFeO3 as SOFC catalysts: Control of oxygen mobility and oxidation activity. Catalysis Today. 2010;**157**(1–4):446-450. DOI: 10.1016/j.

> [36] Miruszewski T, Kamecki B, Lapinski M, Karczewski J. Fabrication, structural and electrical properties of Sr (V,Nb)O3-<sup>δ</sup> perovskite materials. Materials Chemistry and Physics. 2018;

**212**:446-452. DOI: 10.1016/j. matchemphys.2018.03.070

DOI: 10.1016/j.ssi.2013.06.002

Pu J. Electrical conductivity and performance of doped LaCrO3 perovskite oxides for solid oxide fuel cells. Journal of Power Sources. 2008;

**176**(1):82-89. DOI: 10.1016/j. jpowsour.2007.10.053

60525-X

[39] Guo P, Zeng C, Shao Y. Effect of LaCrO3 coating on high temperature oxidation of type 316 stainless steel. Journal of Rare Earths. 2011;**29**(7): 698-701. DOI: 10.1016/S1002-0721(10)

[40] Trasatti S. Water electrolysis: Who first? Journal of Electroanalytical Chemistry. 1999;**476**(1):90-91. DOI: 10.1016/S0022-0728(99)00364-2

[41] Enache S, Dragan M, Varlam M, Petrov K. Electronic percolation threshold of self-standing Ag-LaCoO3 porous electrodes for practical applications. Materials. 2019;**12**(15): 2359. DOI: 10.3390/ma12152359

[42] Enache S, Dragan M, Soare A, Petrov K, Varlam M. Environmentally

[38] Jiang SP, Liu L, Ong KP, Wu P, Li J,

[37] Yaremchenko AA, Brinkmann B, Janssen R, Frade JR. Electrical conductivity, thermal expansion and stability of Y- and Al-substituted SrVO3 as prospective SOFC anode material. Solid State Ionics. 2013;**247–248**:86-93.

cattod.2010.03.037

[30] Zhu C, Nobuta A, Ju YW, Ishihara T, Akiyama T. Solution

10.1016/j.ijhydene.2013.08.007

Ce0.6Mn0.3Fe0.1O2 for anode of SOFC using LaGaO3-based oxide electrolyte. International Journal of Hydrogen Energy. 2013;**38**(30):13419-13426. DOI:

[31] Fu QX, Tietz F, Lersch P, Stover D. Evaluation of Sr- and Mn-substituted LaAlO3 as potential SOFC anode materials. Solid State Ionics. 2006;**177** (11–12):1059-1069. DOI: 10.1016/j.

[32] Xie H, Wei Z, Yang Y, Chen H, Ou X, Lin B, et al. New Gd-Zn codoping enhanced mechanical properties of BaZrO3 proton conductors with high conductivity for IT-SOFCs. Materials Science and Engineering B. 2018;**238– 239**:76-82. DOI: 10.1016/j.mseb.

[33] Shimada H, Yamaguchi T, Sumi H, Nomura K, Yamaguchi Y, Fujishiro Y. Extremely fine structured cathode for solid oxide fuel cells using Sr-doped LaMnO3 and Y2O3-stabilized ZrO2 nano-composite powder synthesized by spray pyrolysis. Journal of Power Sources. 2017;**341**:280-284. DOI: 10.1016/j.jpowsour.2016.12.002

[34] Dragan M, Enache S, Varlam M, Petrov K. Perovskite-type material lanthanum cobaltite LaCoO3: aspects of processing route toward practical applications. In: Cobalt Compounds and

10.5772/intechopen.86260. ISBN: 978-1-

Applications. Rijeka, Croatia: IntechOpen Limited; 2019. DOI:

78984-559-4

**111**

combustion synthesis of

ssi.2006.02.053

2018.12.012

[22] Baek D, Kamegawa A, Takamura H. Mixed conductivity and electrode properties of Mn-doped Bi–Sr–Fe-based perovskite-type oxides. Solid State Ionics. 2013;**253**:211-216. DOI: 10.1016/j. ssi.2013.09.056

[23] Swierczek K, Zajac W, Klimkowicz A, Zheng K, Malikova N, Dabrowski B. Crystal structure and proton conductivity in highly oxygendeficient Ba1xLax(In, Zr, Sn)O3<sup>δ</sup> perovskites. Solid State Ionics. 2015;**275**: 58-61. DOI: 10.1016/j.ssi.2015.02.018

[24] Zang M, Zhao C, Wang Y, Chen S. A review of recent advances in catalytic combustion of VOCs on perovskite-type catalysts. Journal of Saudi Chemical Society. 2019;**23**(6):645-654. DOI: 10.1016/j.jscs.2019.01.004

[25] De Graef M, McHenry ME. Structure of materials: An introduction to crystallography, diffraction and symmetry. Cambridge, United Kingdom: Cambridge University Press; 2007. p. 671. ISBN: 978-0-521-65151-6

[26] Ali R, Yashima M. Space group and crystal structure of the perovskite CaTiO3 from 296 to 1720 K. Journal of Solid State Chemistry. 2005;**178**(9): 2867-2872. DOI: 10.1016/j. jssc.2005.06.027

[27] Goldschmidt VM. Die gesetze der krystallochemie. Die Naturwissenschaften. 1926;**21**:477-485. DOI: 10.1007/bf01507527

[28] Dragan M, Misture S. In-situ analysis of chemical expansion and stability of SOFC cathodes. Materials Research Society Symposium Proceedings. 2014;**1655**:77-82. DOI: 10.1557/opl.2014.413

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

[29] Knyazev AV, Mączka M, Krasheninnikova OV, Ptak M, Syrov EV, Trzebiatowska-Gussowska M. High-temperature X-ray diffraction and spectroscopic studies of some Aurivillius phases. Materials Chemistry and Physics. 2018;**204**:8-17. DOI: 10.1016/j.matchemphys.2017.10.022

[15] Wang WL, Meng Q, Xue Y, Weng X, Sun P, Wu Z. Lanthanide perovskite catalysts for oxidation of chloroaromatics: Secondary pollution and modifications. Journal of Catalysis. 2018;**366**:213-222. DOI: 10.1016/j.

*Perovskite Materials, Devices and Integration*

conductivity measurement. Materials Today: Proceedings. 2018;**5**(14): 27543-27552. DOI: 10.1016/j.

[22] Baek D, Kamegawa A, Takamura H. Mixed conductivity and electrode properties of Mn-doped Bi–Sr–Fe-based perovskite-type oxides. Solid State Ionics. 2013;**253**:211-216. DOI: 10.1016/j.

Klimkowicz A, Zheng K, Malikova N, Dabrowski B. Crystal structure and proton conductivity in highly oxygendeficient Ba1xLax(In, Zr, Sn)O3<sup>δ</sup> perovskites. Solid State Ionics. 2015;**275**: 58-61. DOI: 10.1016/j.ssi.2015.02.018

[24] Zang M, Zhao C, Wang Y, Chen S. A review of recent advances in catalytic combustion of VOCs on perovskite-type catalysts. Journal of Saudi Chemical Society. 2019;**23**(6):645-654. DOI:

matpr.2018.09.074

ssi.2013.09.056

[23] Swierczek K, Zajac W,

10.1016/j.jscs.2019.01.004

2867-2872. DOI: 10.1016/j.

der krystallochemie. Die

DOI: 10.1007/bf01507527

[27] Goldschmidt VM. Die gesetze

[28] Dragan M, Misture S. In-situ analysis of chemical expansion and stability of SOFC cathodes. Materials

Research Society Symposium Proceedings. 2014;**1655**:77-82. DOI:

10.1557/opl.2014.413

Naturwissenschaften. 1926;**21**:477-485.

jssc.2005.06.027

[25] De Graef M, McHenry ME.

Structure of materials: An introduction to crystallography, diffraction and symmetry. Cambridge, United

Kingdom: Cambridge University Press; 2007. p. 671. ISBN: 978-0-521-65151-6

[26] Ali R, Yashima M. Space group and crystal structure of the perovskite CaTiO3 from 296 to 1720 K. Journal of Solid State Chemistry. 2005;**178**(9):

[16] Fang M, Yao X, Li W, Li Y, Shui M, Shu J. The investigation of lithium doping perovskite oxide LiMnO3 as possible LIB anode material. Ceramics International. 2018;**44**(7):8223-8231. DOI: 10.1016/j.ceramint.2018.02.002

[17] Yao C, Zhang H, Liu X, Meng J, Zhang X, Meng F, et al. Characterization

LaBa0.5Sr0.25Ca0.25Co2O5+<sup>δ</sup> as cathode material for intermediate-temperature solid oxide fuel cells. Journal of Solid State Chemistry. 2018;**265**:72-78. DOI:

[18] Parganiha Y, Kaur J, Dubey V, Shrivastavac R. YAlO3:Ce3+ powders:

Microstructures. 2015;**85**:410-417. DOI:

[19] Baig HN, Saluja JK, Haranath D. Investigation of luminescence properties of Dy3+ doped YAlO3 phosphors synthesized through solid state method. Optik. 2016;**127**(20):

[20] Zhang Y, Tso CY, Iñigo JS, Liu S, Miyazaki H, Chao CYH, et al. Perovskite

thermochromic smart window: Advanced optical properties and low transition temperature. Applied Energy. 2019;**254**:113690. DOI: 10.1016/j.

apenergy.2019.113690

**110**

[21] Matsouka C, Zaspalis V,

process—Preparation of dense perovskite membranes and ionic

Nalbandian L. Perovskites as oxygen carriers in chemical looping reforming

of layered double perovskite

10.1016/j.jssc.2018.05.028

Synthesis, characterization, thermoluminescence and optical studies. Superlattices and

10.1016/j.spmi.2015.06.011

9178-9195. DOI: 10.1016/j.

ijleo.2015.12.159

jcat.2018.07.022

[30] Zhu C, Nobuta A, Ju YW, Ishihara T, Akiyama T. Solution combustion synthesis of Ce0.6Mn0.3Fe0.1O2 for anode of SOFC using LaGaO3-based oxide electrolyte. International Journal of Hydrogen Energy. 2013;**38**(30):13419-13426. DOI: 10.1016/j.ijhydene.2013.08.007

[31] Fu QX, Tietz F, Lersch P, Stover D. Evaluation of Sr- and Mn-substituted LaAlO3 as potential SOFC anode materials. Solid State Ionics. 2006;**177** (11–12):1059-1069. DOI: 10.1016/j. ssi.2006.02.053

[32] Xie H, Wei Z, Yang Y, Chen H, Ou X, Lin B, et al. New Gd-Zn codoping enhanced mechanical properties of BaZrO3 proton conductors with high conductivity for IT-SOFCs. Materials Science and Engineering B. 2018;**238– 239**:76-82. DOI: 10.1016/j.mseb. 2018.12.012

[33] Shimada H, Yamaguchi T, Sumi H, Nomura K, Yamaguchi Y, Fujishiro Y. Extremely fine structured cathode for solid oxide fuel cells using Sr-doped LaMnO3 and Y2O3-stabilized ZrO2 nano-composite powder synthesized by spray pyrolysis. Journal of Power Sources. 2017;**341**:280-284. DOI: 10.1016/j.jpowsour.2016.12.002

[34] Dragan M, Enache S, Varlam M, Petrov K. Perovskite-type material lanthanum cobaltite LaCoO3: aspects of processing route toward practical applications. In: Cobalt Compounds and Applications. Rijeka, Croatia: IntechOpen Limited; 2019. DOI: 10.5772/intechopen.86260. ISBN: 978-1- 78984-559-4

[35] Lakshminarayanan N, Kuhn JN, Rykov SA, Millet JMM, Ozkan US. Doped LaFeO3 as SOFC catalysts: Control of oxygen mobility and oxidation activity. Catalysis Today. 2010;**157**(1–4):446-450. DOI: 10.1016/j. cattod.2010.03.037

[36] Miruszewski T, Kamecki B, Lapinski M, Karczewski J. Fabrication, structural and electrical properties of Sr (V,Nb)O3-<sup>δ</sup> perovskite materials. Materials Chemistry and Physics. 2018; **212**:446-452. DOI: 10.1016/j. matchemphys.2018.03.070

[37] Yaremchenko AA, Brinkmann B, Janssen R, Frade JR. Electrical conductivity, thermal expansion and stability of Y- and Al-substituted SrVO3 as prospective SOFC anode material. Solid State Ionics. 2013;**247–248**:86-93. DOI: 10.1016/j.ssi.2013.06.002

[38] Jiang SP, Liu L, Ong KP, Wu P, Li J, Pu J. Electrical conductivity and performance of doped LaCrO3 perovskite oxides for solid oxide fuel cells. Journal of Power Sources. 2008; **176**(1):82-89. DOI: 10.1016/j. jpowsour.2007.10.053

[39] Guo P, Zeng C, Shao Y. Effect of LaCrO3 coating on high temperature oxidation of type 316 stainless steel. Journal of Rare Earths. 2011;**29**(7): 698-701. DOI: 10.1016/S1002-0721(10) 60525-X

[40] Trasatti S. Water electrolysis: Who first? Journal of Electroanalytical Chemistry. 1999;**476**(1):90-91. DOI: 10.1016/S0022-0728(99)00364-2

[41] Enache S, Dragan M, Varlam M, Petrov K. Electronic percolation threshold of self-standing Ag-LaCoO3 porous electrodes for practical applications. Materials. 2019;**12**(15): 2359. DOI: 10.3390/ma12152359

[42] Enache S, Dragan M, Soare A, Petrov K, Varlam M. Environmentally friendly methods for high quality lanthanum cobaltite perovskite catalyst synthesis. Progress of Cryogenics and Isotopes Separation. 2019;**22**(1):39

[43] Enache S, Dragan M, Soare A, Ebrasu DI, Zaulet A, Varlam M, et al. One step solid-state synthesis of lanthanum cobalt oxide perovskites as catalysts for oxygen evolution in alkaline media. Bulgarian Chemical Communications. 2018;**50**(A):127-132

[44] Jiang SP. A comparison of O2 reduction reactions on porous (La,Sr) MnO3 and (La,Sr)(Co,Fe)O3 electrodes. Solid State Ionics. 2002;**146**(1–2):1-22. DOI: 10.1016/S0167-2738(01)00997-3

[45] Manwar NR, Borkar RG, Khobragade R, Rayalu SS, Jain SL, Bansiwal AK, et al. Efficient solar photoelectrochemical hydrogen generation using nanocrystalline CeFeO3 synthesized by a modified microwave assisted method. International Journal of Hydrogen Energy. 2017;**42**(16): 10931-10942. DOI: 10.1016/j. ijhydene.2017.01.227

[46] Petric A, Huang P, Tietz F. Evaluation of La–Sr–Co–Fe–O perovskites for solid oxide fuel cells and gas separation membranes. Solid State Ionics. 2002;**135**(1–4):719-725. DOI: 10.1016/S0167-2738(00)00394-5

[47] Tietz F, Arul Raj I, Zahid M, Mai A, Stover D. Survey of the quasi-ternary system La0.8Sr0.2MnO3–La0.8Sr0.2CoO3– La0.8Sr0.2FeO3. Progress in Solid State Chemistry. 2007;**35**(2–4):539-543. DOI: 10.1016/j.progsolidstchem.2007.01.028

[48] Ullmann H, Trofimenko N, Tietz F, Stover D, Ahmad-Khanlou A. Correlation between thermal expansion and oxide ion transport in mixed conducting perovskite-type oxides for SOFC cathodes. Solid State Ionics. 2000; **138**(1–2):79-90. DOI: 10.1016/ S0167-2738(00)00770-0

[49] Choi S, Yoo S, Kim J, Park S, Jun A, Sengodan S, et al. Highly efficient and robust cathode materials for lowtemperature solid oxide fuel cells: PrBa0.5Sr0.5Co2-xFexO5. Scientific Reports. 2013;**3**:2426. DOI: 10.1038/ srep02426

[55] Kim J, Chen X, Shih PC, Yang H. Porous perovskite-type lanthanum cobaltite as electrocatalysts toward oxygen evolution reaction. ACS Sustainable Chemistry & Engineering. 2017;**5**(11):10910-10917. DOI: 10.1021/

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

[56] Tijare SN, Joshi MV, Padole PS,

[57] Puangpetch T, Sreethawong T, Yoshikawa S, Chavadej S. Hydrogen production from photocatalytic water splitting over mesoporous-assembled

photocatalysts. Journal of Molecular Catalysis A: Chemical. 2009;**312**(1–2): 97-106. DOI: j.molcata.2009.07.012

acssuschemeng.7b02815

Mangrulkar PA, Rayalu SS, Labhsetwar NK. Photocatalytic hydrogen generation through water splitting on nano-crystalline LaFeO3 perovskite. International Journal of Hydrogen Energy. 2012;**37**(13): 10451-10456. DOI: 10.1016/j.

ijhydene.2012.01.120

SrTiO3 nanocrystal-based

**113**

[50] Dragan M, Enache S, Soare A, Petrov K, Varlam M. LaCoO3 perovskite-type oxide: Synthesis and characterization towards practical applications. Progress of Cryogenics and Isotopes Separation. 2018;**21**(2):49-56

[51] Ebrasu DI, Zaulet A, Enache S, Dragan M, Carcadea E, Varlam M, et al. Electrochemical characterization of metal oxide as catalysts oxygen evolution in alkaline media. Bulgarian Chemical Communications. 2018;**50**(A): 133-138

[52] Humayun M, Sun N, Raziq F, Zhang X, Yan R, Li Z, et al. Synthesis of ZnO/Bi-doped porous LaFeO3 nanocomposites as highly efficient nano-photocatalysts dependent on the enhanced utilization of visible-lightexcited electrons. Applied Catalysis B: Environmental. 2018;**231**:23-33. DOI: 10.1016/j.apcatb.2018.02.060

[53] Ibarra-Rodriguez LI, Huerta-Flores AM, Mora-Hernandez JM, Torres-Martínez LM. Photocatalytic evolution of H2 over visible-light active LaMO3 (M: Co, Mn, Fe) perovskite materials: Roles of oxygenated species in catalytic performance. Journal of Physics and Chemistry of Solids. 2020;**136**:109189. DOI: 10.1016/j.jpcs.2019.109189

[54] Egelund S, Caspersen M, Nikiforov A, Moller P. Manufacturing of a LaNiO3 composite electrode for oxygen evolution in commercial alkaline water electrolysis. International Journal of Hydrogen Energy. 2016;**41**(24): 10152-10160. DOI: 10.1016/j.ijhydene. 2016.05.013

*Perovskite-Based Materials for Energy Applications DOI: http://dx.doi.org/10.5772/intechopen.91271*

[55] Kim J, Chen X, Shih PC, Yang H. Porous perovskite-type lanthanum cobaltite as electrocatalysts toward oxygen evolution reaction. ACS Sustainable Chemistry & Engineering. 2017;**5**(11):10910-10917. DOI: 10.1021/ acssuschemeng.7b02815

friendly methods for high quality lanthanum cobaltite perovskite catalyst synthesis. Progress of Cryogenics and Isotopes Separation. 2019;**22**(1):39

*Perovskite Materials, Devices and Integration*

[49] Choi S, Yoo S, Kim J, Park S, Jun A, Sengodan S, et al. Highly efficient and robust cathode materials for lowtemperature solid oxide fuel cells: PrBa0.5Sr0.5Co2-xFexO5. Scientific Reports. 2013;**3**:2426. DOI: 10.1038/

[50] Dragan M, Enache S, Soare A, Petrov K, Varlam M. LaCoO3 perovskite-type oxide: Synthesis and characterization towards practical applications. Progress of Cryogenics and Isotopes Separation. 2018;**21**(2):49-56

[51] Ebrasu DI, Zaulet A, Enache S, Dragan M, Carcadea E, Varlam M, et al. Electrochemical characterization of metal oxide as catalysts oxygen evolution in alkaline media. Bulgarian Chemical Communications. 2018;**50**(A):

[52] Humayun M, Sun N, Raziq F, Zhang X, Yan R, Li Z, et al. Synthesis of

ZnO/Bi-doped porous LaFeO3 nanocomposites as highly efficient nano-photocatalysts dependent on the enhanced utilization of visible-lightexcited electrons. Applied Catalysis B: Environmental. 2018;**231**:23-33. DOI:

10.1016/j.apcatb.2018.02.060

[54] Egelund S, Caspersen M,

2016.05.013

Nikiforov A, Moller P. Manufacturing of a LaNiO3 composite electrode for oxygen evolution in commercial alkaline water electrolysis. International Journal of Hydrogen Energy. 2016;**41**(24): 10152-10160. DOI: 10.1016/j.ijhydene.

[53] Ibarra-Rodriguez LI, Huerta-Flores AM, Mora-Hernandez JM, Torres-Martínez LM. Photocatalytic evolution of H2 over visible-light active LaMO3 (M: Co, Mn, Fe) perovskite materials: Roles of oxygenated species in catalytic performance. Journal of Physics and Chemistry of Solids. 2020;**136**:109189. DOI: 10.1016/j.jpcs.2019.109189

srep02426

133-138

[43] Enache S, Dragan M, Soare A, Ebrasu DI, Zaulet A, Varlam M, et al. One step solid-state synthesis of lanthanum cobalt oxide perovskites as catalysts for oxygen evolution in alkaline media. Bulgarian Chemical Communications. 2018;**50**(A):127-132

[44] Jiang SP. A comparison of O2 reduction reactions on porous (La,Sr) MnO3 and (La,Sr)(Co,Fe)O3 electrodes. Solid State Ionics. 2002;**146**(1–2):1-22. DOI: 10.1016/S0167-2738(01)00997-3

[45] Manwar NR, Borkar RG, Khobragade R, Rayalu SS, Jain SL, Bansiwal AK, et al. Efficient solar photoelectrochemical hydrogen generation

using nanocrystalline CeFeO3

[46] Petric A, Huang P, Tietz F. Evaluation of La–Sr–Co–Fe–O

perovskites for solid oxide fuel cells and gas separation membranes. Solid State Ionics. 2002;**135**(1–4):719-725. DOI: 10.1016/S0167-2738(00)00394-5

[47] Tietz F, Arul Raj I, Zahid M, Mai A, Stover D. Survey of the quasi-ternary system La0.8Sr0.2MnO3–La0.8Sr0.2CoO3– La0.8Sr0.2FeO3. Progress in Solid State Chemistry. 2007;**35**(2–4):539-543. DOI: 10.1016/j.progsolidstchem.2007.01.028

[48] Ullmann H, Trofimenko N, Tietz F,

Correlation between thermal expansion and oxide ion transport in mixed conducting perovskite-type oxides for SOFC cathodes. Solid State Ionics. 2000;

Stover D, Ahmad-Khanlou A.

**138**(1–2):79-90. DOI: 10.1016/ S0167-2738(00)00770-0

**112**

ijhydene.2017.01.227

synthesized by a modified microwave assisted method. International Journal of Hydrogen Energy. 2017;**42**(16): 10931-10942. DOI: 10.1016/j.

[56] Tijare SN, Joshi MV, Padole PS, Mangrulkar PA, Rayalu SS, Labhsetwar NK. Photocatalytic hydrogen generation through water splitting on nano-crystalline LaFeO3 perovskite. International Journal of Hydrogen Energy. 2012;**37**(13): 10451-10456. DOI: 10.1016/j. ijhydene.2012.01.120

[57] Puangpetch T, Sreethawong T, Yoshikawa S, Chavadej S. Hydrogen production from photocatalytic water splitting over mesoporous-assembled SrTiO3 nanocrystal-based photocatalysts. Journal of Molecular Catalysis A: Chemical. 2009;**312**(1–2): 97-106. DOI: j.molcata.2009.07.012

**115**

Section 3

Other Applications

of Perovskite

Section 3
