Abstract:

Au catalysts supported on an oxide show excellent activity in CO oxidation under moderate conditions. Many experiments and theoretical calculations have shown the important role of the interface between Au and the oxide support during CO oxidation. Inverse catalysts provide an alternative way to probe the role of the interface. We used Al₂O₃/Au(111) as a model inverse catalyst in this study, and used density functional theory to investigate the properties of Al₂O₃/Au(111), the interface between Al₂O₃ and Au(111), the adsorption of O₂, and CO oxidation over Al₂O₃/Au(111). Our theoretical calculations show that small Al₂O₃ clusters are strongly bound on the Au(111) surface as a result of charge transfer. The results for O₂ adsorption on different sites indicate that the interfacial site is the most stable one because of simultaneous bonding of O₂ with Au and Al atoms. The full catalytic cycles for CO oxidation by O₂ by either an association or dissociation pathway were investigated. Oxidation in the association pathway is significantly easier than that in the dissociation one; the participation of CO makes dissociation of the adsorbed O₂ easier. This study reveals not only the origin of inverse catalysts for CO oxidation but also the role of the interface in CO oxidation on Au catalysts.

Key words: Inverse catalyst, Au catalyst, CO oxidation, Density functional theory, Interfacial site