A Convenient Route for Au@Ti–SiO₂ Nanocatalyst Synthesis and Its Application for Room Temperature CO Oxidation

Abstract

Small gold nanoparticles of size less than 5 nm encapsulated inside titanium modified silica shell have been reported. Here, a modified sol–gel method, which is a one-step process, produces Au@Ti–SiO2 nanocatalyst with a good control of titanium loading. With a titanium loading of 0.9 and 2.2 wt % in silica, unprecedented low temperature activity (full conversion) is observed for this catalyst for CO oxidation reaction compared to Au@SiO2 catalyst. A combination of optimum sized gold nanoparticles with a large amount of oxygen vacancies created due to Ti incorporation in silica matrix is considered to be the reason for this enhanced catalytic activity. The size of gold nanoparticles is maintained even after high temperature pretreatments, which show the benefit of encapsulation. The effect of the various pretreatments on the catalytic activity has also been reported.

Mechanisms for Catalytic CO Oxidation on SiAun (n = 1–5) Cluster

“…One of the reactions that has received the most attention in the field of heterogeneous catalysis is CO oxidation [ 33 , 34 , 35 ]. Both experimental and theoretical studies have investigated the catalysis of CO oxidation by cluster [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. Payam et al [ 36 ] found that the catalytic activity of Pd/TiO 2 /Ti metal-supported catalysts was improved by the introduction of Zn, especially at Pd:Zn = 2:1, which reduced the binding energy of CO on the surface and improved the dissociative adsorption of oxygen, which facilitated the oxidation of CO.…”

“…This is the first report of CO oxidation using Au/POM catalysts, and their use has the potential to be extended to various gas-phase reactions. Soni et al [ 41 ] used a novel synthesis method for the preparation of Au@Ti-SiO 2 with an optimum gold NP size (3–5 nm) using the sol–gel method in one step; for Si/Ti ratios of 10 (ATS 10) and 50 (ATS 50), the activity dramatically increased after treatment in a nitrogen flow, with almost 100% conversion of CO at room temperature.…”