**2.2 Catalyst preparation**

All catalyst powders were prepared using the EDTA-citrate auto combustion method [5]. Metal nitrates were employed as desired metal pre-cursors for support. A 2 g-scale preparation for LaFe1-xCuxO3-Δ is described below as an example. Lanthanum nitrate (La(NO3)3·6H2O) was dissolved in deionized water (100 mL), followed by mixing into an aqueous solution of copper and iron nitrates in stoichiometric ratios at room temperature. EDTA (3.8 g) dissolved in an aqueous NH3 solution was then dropped into the mixed solution, followed by the addition of solid citric acid (3.7 g) upon stirring. Molar ratio of total metal ions (La + Fe-Cu), EDTA, and citrate is 1.0:1.0:1.5, respectively. NH4OH was used to adjust the pH of the solution to the desired value of 11 [12–14]. The solution was then heated above 80°C slowly and became dark brown after being brown-orange at the beginning.

**83**

**Figure 4.**

*Zoomed in image of XRD LFCO-10.*

*Reducing Green House Effect Caused by Soot via Oxidation Using Modified LaFe1-xCuxO3…*

The gel was placed in a hot air oven at 200°C for 12 h to combust and convert into flaking solid powders. Next, the powders were crushed and calcined at 800°C for 6 h in air to yield LaFe1-xCuxO3-Δ which was ground and solid power was obtained. The preparation method for undoped LFO samples is the same as above (**Figure 3**) [13].

As shown in **Figure 4**, doping of copper of the perovskite did not affect the crystal structures of LaFe1-xCuxO3 samples (LFCO-10–LFCO-20). The peaks were in negligible deviation to the peaks of LFO. The characteristic diffraction peaks were at 22.6°, 32.2°, 38.0°, 39.6°, 46.3°, 53.3°, 57.4°, 67.4°, and 76.7° in the diffraction data of all samples can be correlated to the indices of the crystal planes of (101), (121), (112), (220), (141), (311), (240), (242), and (204), signifying that the fabricated samples were finely crystallized with three-dimensional orthorhombic structure (JCPDS No. 37-1493) [15, 16]. **Figure 4** zooms in the XRD graph of LFCO-10 and contrasts it with

the pure LFO synthesized in-situ and in agreement with the JCPDS data.

decreased with increasing amount of Cu dopant.

oxidation reaction [15].

**Table 1** shown below depicts the a, b, c values for lattice constants of the perovskite LaFeO3 and [17] LaFe1-xCuxO3. The introduction of Cu(II) with a larger ionic radius (0.730 Å) to replace Fe(III) with smaller ionic radius (0.645 Å) did not result in the expansion of LFO unit-cell [18, 19]. The smaller cell volume of LaFe1-xCuxO3 might be caused by the defects in the form of anionic vacancies, which maintained the electroneutrality in LaFe1-xCuxO3 [17, 20–26]. In **Table 1**, the crystallite sizes of Cu-doped LFO samples were smaller than that of undoped sample and

This concurs with the literature, it shows that increasing Cu doping could cause lattice distortion and hinders the growth of large crystallites in the samples. The large degree of crystallinity with minute defects fosters the reduction in the recombination of electron–hole pairs, leading to enhanced efficiency of the soot

*DOI: http://dx.doi.org/10.5772/intechopen.90460*

**3. Results**

**Figure 3.** *XRD plot of LaFeO3 doped with copper on B site.*

The gel was placed in a hot air oven at 200°C for 12 h to combust and convert into flaking solid powders. Next, the powders were crushed and calcined at 800°C for 6 h in air to yield LaFe1-xCuxO3-Δ which was ground and solid power was obtained. The preparation method for undoped LFO samples is the same as above (**Figure 3**) [13].
