Potassium and Water Coadsorption on TiO₂(110): OH-Induced Anchoring of Potassium and the Generation of Single-Site Catalysts

Potassium deposition on TiO₂(110) results in reduction of the substrate and formation of loosely bound potassium species that can move easily on the oxide surface to promote catalytic activity. The results of density functional calculations predict a large adsorption energy (∼3.2 eV) with a small barrier (∼0.25 eV) for diffusion on the oxide surface. In scanning tunneling microscopy images, the adsorbed alkali atoms lose their mobility when in contact with surface OH groups. Furthermore, K adatoms facilitate the dissociation of water on the titania surface. The K-(OH) species generated are good sites for the binding of gold clusters on the TiO₂(110) surface, producing Au/K/TiO₂(110) systems with high activity for the water-gas shift.