Calculations of CO Oxidation over a Au/TiO2 Catalyst: A Study of Active Sites, Catalyst Deactivation, and Moisture Effects

The reaction mechanism of CO oxidation on Au/TiO2 catalysts remains elusive. Here, we employ density functional theory calculations to gain an understanding of several important aspects of the system, including CO adsorption, the active oxygen species, catalyst deactivation, and the promoting effect of moisture on catalytic activity. Distinct from previous theoretical studies, which tend to address these questions individually, here we construct a model of the catalytic system which can address all of the issues mentioned. For this, we have considered the complex interactions among reactants, products, and catalysts under reaction conditions. The main findings of our present study are (1) the Au/TiO2 interface boundary can be easily oxidized, (2) CO adsorption on oxidized Au results in the formation of O−Au−CO species, (3) surface lattice oxygen on a TiO2 support is the active oxygen species, (4) CO2 binds strongly on the Otop/Ti5c site, forming carbonate that blocks the active site, and finally (5) water can accelerate O2 dissociation and carbonate decomposition. The results of our theoretical model are compared with existing experimental observations and found to be largely consistent with them.