Platinum Nanoparticles Supported on Anatase Titanium Dioxide as Highly Active Catalysts for Aerobic Oxidation under Visible Light Irradiation

Visible light irradiation (lambda >450 nm) of platinum (Pt) nanoparticles supported on anatase titanium dioxide (TiO2) promotes efficient aerobic oxidation at room temperature. This occurs via the electronic excitation of Pt particles by visible light followed by the transfer of their electrons to anatase conduction band. The positively charged Pt particles oxidize substrates, whereas the conduction band electrons are consumed by the reduction of molecular oxygen. The activity of this photocatalysis depends on the height of Schottky barrier and the number of perimeter Pt atoms created at the Pt/anatase heterojunction, which are affected by the amount of Pt loaded and the size of Pt particles. The catalyst loaded with 2 wt % Pt, containing 3-4 nm Pt particles, creates a relatively low Schottky barrier and a relatively large number of perimeter Pt atoms and, hence, facilitates smooth Pt -> anatase electron transfer, resulting in very high photocatalytic activity. This catalyst is successfully activated by sunlight and enables efficient and selective aerobic oxidation of alcohols at ambient temperature.