Reaction Mechanism of the Low-Temperature Water-Gas Shift Reaction on Au/TiO2 Catalysts

The redox and associative mechanisms for the low temperature water gas shift (WGS) reaction on Au/TiO2 catalysts are thoroughly examined by density functional theory calculations and microkinetic studies. For the redox mechanism, we have observed that the presence of a gold cluster and extra oxygen vacancies on a TiO2 surface is vital for the WGS reaction, especially for the process of H-2, release. For the associative mechanism via intermediate species, it is very hard for COOH to be generated in the WGS reaction. HCOO could be generated, while HCOO should only be a product of side reactions because of the difficulty in H-2 release. The present results indicate that the WGS reaction on Au/TiO2 catalysts can be well explained by the redox mechanism. The present understanding of the mechanism should open a new door for catalyst design in WGS reactions.