As a promising route for large-scale ${\mathrm{H}}_2$ production, the water-gas-shift reaction (WGS, $\mathrm{CO}+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{CO}}_2+{\mathrm{H}}_2$) on ceria-supported Au catalysts is of enormous potential in efforts to move towards a hydrogen economy. Recent research suggests that this reaction is in fact catalyzed by Au cations instead of the conventionally regarded metallic Au particles. Here density functional theory calculations demonstrate that the presence of empty localized nonbonding $f$ states in ${\mathrm{CeO}}_2$ permits the oxidation of Au, enabling subsequent CO adsorption. A feasible reaction pathway leading to ${\mathrm{H}}_2$ production is identified, and it is concluded that four to six atom Au clusters at the O-vacancy sites of ceria catalyze the WGS reaction.

• Received 26 January 2005

DOI:https://doi.org/10.1103/PhysRevLett.94.196102