Activity of CeOx and TiOx nanoparticles grown on Au(111) in the water-gas shift reaction

The high performance of Au-CeO2 and Au-TiO2 catalysts in the water- gas shift ( WGS) reaction ( H2O + CO --> H-2 + 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 TiO2-x/Au( 111) and CeO2-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.