Role ofAu+in Supporting and ActivatingAu7onTiO2(110)

The adhesion properties and catalytic activity of rutile ${\mathrm{TiO}}_{2}(110)$-supported ${\mathrm{Au}}_{7}$ nanoclusters in different oxidation states are investigated by means of density functional theory. The calculations cover both surface science conditions of reduced ${\mathrm{TiO}}_{2}$ and real catalyst conditions of oxidized (alkaline) ${\mathrm{TiO}}_{2}$ supports. Large adhesion energies of ${\mathrm{Au}}_{7}$ are found only when modeling real catalysts where the cluster becomes cationic with ${\mathrm{Au}}^{+}$ ions in Au-O or Au-OH bonds. The full catalytic cycle for oxidation of CO by ${\mathrm{O}}_{2}$ over ${\mathrm{Au}}_{7}$ on alkaline ${\mathrm{TiO}}_{2}(110)$ is calculated and found to involve only small activation barriers. In the presence of the CO reductant, the ${\mathrm{Au}}^{+}$ sites are capable of cycling between bonding of atomic and molecular oxygen. We confirm our findings by comparison of calculated and experimental infrared stretch frequency data for adsorbed CO.