Adsorption of oxygen and CO oxidation on Au/anatase(001) catalysts. A DFT+U study

Abstract

DFT calculations were performed to probe CO oxidation over Au/TiO₂ catalysts by adsorbed oxygen. Adsorption dynamics of the O₂ molecule like geometric properties, binding energy, electronic structure and dissociation mechanism were investigated. The calculations indicate that adsorption of oxygen is most favorable at the periphery of Au/TiO₂ with a binding energy of −139 kJ mol⁻¹. The electronic structure of the adsorbed oxygen indicates that the adsorption is governed by the p–d hybridization of oxygen and Au, with a small contribution from Ti atoms of the support. Upon adsorption of oxygen, the Au cluster loses 0.92 e to adsorbed oxygen. The charge lost by the Au cluster is equally shared by both oxygen atoms (−0.46 e each). Dissociation of oxygen into oxygen adatoms is exothermic and activated by 56 kJ mol⁻¹. Finally, the CO oxidation by adatoms is highly exothermic and activated by an activation barrier of 39.4 kJ mol⁻¹. The calculations show that both oxygen dissociation and CO oxidation are fairly easy on the Au/anatase catalyst.