Activity of CeO x and TiO x Nanoparticles Grown on Au(111) in the Water-Gas Shift Reaction

Abstract

The high performance of Au-CeO₂ and Au-TiO₂ catalysts in the water-gas shift (WGS) reaction (H₂O + CO→H₂ + CO₂) relies heavily on the direct participation of the oxide in the catalytic process. Although clean Au(111) is not catalytically active for the WGS, gold surfaces that are 20 to 30% covered by ceria or titania nanoparticles have activities comparable to those of good WGS catalysts such as Cu(111) or Cu(100). In TiO_2-x/Au(111) and CeO_2-x/Au(111), water dissociates on O vacancies of the oxide nanoparticles, CO adsorbs on Au sites located nearby, and subsequent reaction steps take place at the metal-oxide interface. In these inverse catalysts, the moderate chemical activity of bulk gold is coupled to that of a more reactive oxide.