The effect of reactants adsorption and products desorption for Au/TiO2 in catalyzing CO oxidation

Abstract

Supported gold catalysts exhibit very high activity for CO oxidation. However, there is lack of systematic study for supports effect on reactants adsorption and products desorption. Herein, we successfully prepared supported gold catalysts on TiO2 matrix exposing either {1 0 1} or {0 0 1} crystal plane (labeled as Au/TiO2-1 0 1 and Au/TiO2-0 0 1 respectively) by deposition-precipitation (DP) method. It is found that the reactivity of Au/TiO2-1 0 1 was much higher than Au/TiO2-0 0 1 in CO oxidation reaction (9.33 × 10−3 molCOgAu−1 s−1vs. 6.23 × 10−4 molCOgAu−1 s−1 at 30 °C). The gold nanoparticles (∼2 nm) were detected as sole gold species in Au/TiO2-1 0 1, while not only gold nanoparticles (∼4 nm) but also clusters (∼1.3 nm) were present in Au/TiO2-0 0 1. The difference in gold status induced different CO adsorption situations that CO was more effectively adsorbed on gold nanoparticles in Au/TiO2-1 0 1 which existed more Au0 site. Meanwhile, we revealed that the bidentate carbonate, which could either block active sites for the reaction or hinder access of reactants, were adsorbed much more strongly on TiO2-0 0 1. While on TiO2-1 0 1, bicarbonate was the main surface species which was easier decomposed to form CO2. Therefore, the differences between Au/TiO2-1 0 1 and Au/TiO2-0 0 1 in the efficiency of CO adsorption and the ability of CO2 desorption resulted in disparate reactivity. We reasonably gave the deep insight into the support effect that was intrinsically related to the adsorption and desorption behavior of surface species on the catalyst.