Size-Dependent Reaction Pathways of Low-Temperature CO Oxidation on Au/CeO2 Catalysts

Via a comprehensive time-resolved operando-DRIFTS study of the evolutions of various surface species on Au/CeO2 catalysts with Au particle sizes ranging from 1.7 +/- 0.6 to 3.7 +/- 0.9 nm during CO oxidation at room temperature, we have successfully demonstrated size-dependent reaction pathways and their contributions to the catalytic activity. The types and concentrations of chemisorbed CO(a), carbonate, bicarbonate, and formate species formed upon CO adsorption, their intrinsic oxidation/decomposition reactivity, and roles in CO oxidation vary with the size of the supported Au particles. The intrinsic oxidation reactivity of CO(a) does not depend much on the Au particle size, whereas the intrinsic decomposition reactivity of carbonate, bicarbonate, and formate species strongly depend on the Au particle size and are facilitated over Au/CeO2 catalysts with large Au particles. These results greatly advance the fundamental understanding of the size effect of Au/CeO2 catalysts for low-temperature CO oxidation.