**1.2 Au-M bimetallic nanoparticles on various silica support for the CO oxidation reaction**

Recent research reveals that bimetallic nanoparticles often exhibit better catalytic performances compared with the monometallic counterparts. This has led to a great interest in both academic and industrial fields. The interaction between the two components of bimetallic catalysts is mostly understood in terms of assemble and ligand effects, where one component may act as a spacer to separate the active sites [78] or as an electronic modifier to the other component [79]. The catalytic performances of bimetallic nanoparticles are subject to depend on several factors,

**41**

*Silica-Supported Gold Nanocatalyst for CO Oxidation DOI: http://dx.doi.org/10.5772/intechopen.80620*

the activity of the reaction (**Table 2**).

Silica SBA-15

Hexagonal mesoporous silica (HMS)

Au-Ag Silica 4.9–5.6

Au-Cu SiO2 2 (Au-Cu) 14 (Au-Cu

SiO2 4.6

MCM 5

(Au-Cu)

(Au-Ag)

(Au-Ag)

Au-Fe SBA-15 0.5–0.8 <4 20 [95]

Au-Ce SBA-15 1.3–2.7 4.4–26 160–170 [101]

Au-Al SBA-15 3–17 3 80 [103]

**Bimetallic catalyst**

such as nanostructure, surface composition, particle size, and shape. The most important features which differentiate a bimetallic catalyst from monometallic catalysts are the surface compositions and tunable nanostructures. A bimetallic nanostructure could be a random alloy, a core-shell structure, or just mixed mono-

There are several literature reports in account, for the effect of second metals like Ti [78–88], Cu [89–92], Fe [93–95], Ag [96–98], Ce [99–100], Al [101–102], Co [103], Pd [104], Pt [105], and Sn [106] to the Au NPs for the activity of CO oxidation. It has been established that, synergistic effects of both the metals improve the catalytic performance in CO oxidation reaction. Type of bimetallic catalysts, support, size of the Au NPs, and the gold loading are showing remarkable effects on

**Au size (nm) Temperature (°C) Ref.**

1.8–2.5 2.9–10.2 120 (T50) [90]

4 (Au-Cu) 25–300 [93]

300 (Au 0.4 wt%)

150 [91]

0 [98]

30 [100]

[96]

metallic nanoparticles, which give rise to different catalytic activities.

**Support Au loading** 

**(wt%)**

Au-Ti Silica aerogel 0.1–20 2.0 −50–70 [80]

Silica aerogel 3.4–6.7 1.4–6.4 −50–70 [81] Silica aerogel 5.0 2.0 [82] SBA-15 1.7–3.6 3.0–15 200 [83] SBA-15 — 0.8–1.0 −40 (T50) [84] SBA-15 1 3–4 50 [85] MCM-48 3.0–7.5 <1 17–27 [86] MCM-48 — — <0 [87] Silica 1.4–2.0 6.6–7.2 160 [88] MCM-41 — <3 350 [89]

colloidal)

SiO2 2 (Au-Cu) 10 300 [92]

SBA-15 6 (Au-Cu) ~3 0 [94]

Mesoporous silica 0.4–2.0 >5 −5 [97]

~3 (Au-Ag)

MCM 8 (Au-Ag) 6–7 RT [99]

SBA-15 2 3–6 150–350 [102]

SBA-15 15–20 2.7 80 [104]

4–6 (Au-Ag)

0.4–5.1 3.3–4.5 25 (Au 5.1 wt%)–

*Silica-Supported Gold Nanocatalyst for CO Oxidation DOI: http://dx.doi.org/10.5772/intechopen.80620*

*Gold Nanoparticles - Reaching New Heights*

Yang et al. reported an improved strategy for the preparation of SBA-15 supported metal nanoparticles [74]. Supported Au nanoparticle catalyst Au/SBA-15 exhibited significantly higher activities in the oxidation of CO by molecular oxygen after adding polyvinylpyrrolidone (PVP) to the reaction system. Earlier, it has been reported that, PVP could strongly interact with the soluble Au NPs in water solvent,

*1-NH2-b1 after H2 treatment at 300°C for 1 h. Reproduced with permission, copyright 2018, Wiley.*

*) for CO oxidation over Au/KCC-1-NH2-a1, Au/KCC-1-NH2-a2 and Au/KCC-*

Recently, Behm et al. have developed an improved catalytic system for the stability of metal oxide-supported Au catalysts for low-temperature CO oxidation reaction [77]. Effect of mesoporous silica SBA-15 substrate on the catalytic activity and stability of Au/TiO2 catalysts has been explored, where the catalyst system composed of a SBA-15 support surface modified by a monolayer of TiOx and Au NPs on top. Later, TiOx surface layers were systematically increased without changing the Au loading and particle size. Kinetic measurements were calculated at three different temperatures (30, 80, and 180°C). It was noted that catalyst surface modification with Ti has distinct effect, the performance of these catalysts increases

significantly with Ti concentration and also with reaction temperature.

**1.2 Au-M bimetallic nanoparticles on various silica support for the CO** 

Recent research reveals that bimetallic nanoparticles often exhibit better catalytic performances compared with the monometallic counterparts. This has led to a great interest in both academic and industrial fields. The interaction between the two components of bimetallic catalysts is mostly understood in terms of assemble and ligand effects, where one component may act as a spacer to separate the active sites [78] or as an electronic modifier to the other component [79]. The catalytic performances of bimetallic nanoparticles are subject to depend on several factors,

leading to high activity in oxidation reaction [75–76].

**40**

**Figure 9.**

*Turn over frequency (TOF S<sup>−</sup><sup>1</sup>*

**oxidation reaction**

such as nanostructure, surface composition, particle size, and shape. The most important features which differentiate a bimetallic catalyst from monometallic catalysts are the surface compositions and tunable nanostructures. A bimetallic nanostructure could be a random alloy, a core-shell structure, or just mixed monometallic nanoparticles, which give rise to different catalytic activities.

There are several literature reports in account, for the effect of second metals like Ti [78–88], Cu [89–92], Fe [93–95], Ag [96–98], Ce [99–100], Al [101–102], Co [103], Pd [104], Pt [105], and Sn [106] to the Au NPs for the activity of CO oxidation. It has been established that, synergistic effects of both the metals improve the catalytic performance in CO oxidation reaction. Type of bimetallic catalysts, support, size of the Au NPs, and the gold loading are showing remarkable effects on the activity of the reaction (**Table 2**).



#### **Table 2.**

*Au-M bimetallic catalysts with different types of silica supports for the CO oxidation reaction.*
