Identification of the Catalytic Site at the Interface Perimeter of Au Clusters on Rutile TiO₂(110)

We present a density functional theory study of the CO oxidation reaction at a Au₂₄ cluster supported on a rutile TiO₂(110) slab. The global minimum structure of the Au₂₄ cluster is found using a genetic algorithm search. Catalytic sites are found at the perimeter of the Au–TiO₂ interface but with strong dependence on the surface direction. It is shown how the CO oxidation reaction only happens along the [11̅0] direction of the support and not along the [001] direction. This effect is attributed to a too weak CO binding energy along the [001] direction caused by the charge state and Au–Au coordination of the Au atoms along this direction.