Influence of Support Hydroxides on the Catalytic Activity of Oxidized Gold Clusters

Gold oxide nanoparticles were prepared on the native surface and a hydroxylated surface of a nonporous TiO₂ support (Degussa P25). Scanning transmission electron microscopy shows the formation of similarly sized clusters on both support materials (1.86 and 1.61 nm clusters on the native oxide and the hydroxylated oxide respectively). X-ray absorption near-edge spectroscopy and X-ray photoelectron spectroscopy clearly indicate the formation of Au³⁺-rich oxide nanoparticles. Despite the similar cluster sizes and oxidation states, the gold oxide clusters grown on the hydroxylated surface were at least 180 times more catalytically active for the oxidation of carbon monoxide than those grown on the native oxide surface. Thus hydroxides, which are incidentally introduced during the solution-phase synthesis of gold catalysts, appear to play a dominant, but previously largely unrecognized, role in the catalytic properties of both oxidized and metallic gold particles.