Theoretical investigation of the variations in CO oxidation activity of Au/ZnO catalysts under different pretreatment conditions

Abstract Au clusters supported on reducible metal oxides exhibit high catalytic activity for CO oxidation even at temperatures below 273 K. In a previous study, the activation barrier for CO oxidation over Au/ZnO exhibited a significant variation at approximately 253 K when the catalyst was prepared under conditions including H2 reduction, whereas no such change was observed when it was prepared under air-oxidation conditions. Herein, this variation was elucidated by examining the reaction mechanisms of CO oxidation over Au/ZnO catalysts with stoichiometric and reduced surfaces using density functional theory calculations. The results show that catalytic reactions were promoted on the reduced surface compared with those on the stoichiometric surface because of the strong activation of adsorbed O2. Furthermore, the variation in the activation barriers for CO oxidation over Au/ZnO with H2 reduction pretreatment above 253 K may be attributed to the change from a reduced surface to a stoichiometric surface.