Photocatalytic oxidation of oxalic acid enhanced by silver deposition on a TiO2 surface

Photooxidation of oxalic acid over TiO2 surface in the presence of silver ion was studied. Simultaneous deposition of silver and oxidation of oxalic acid were followed under irradiation of aqueous suspensions of pH 2.5–3.5. The rate of the reduction of Ag+ was increased by the progress of silver deposition until a considerable depletion of the silver ion in the liquid phase was achieved. Then it was slowed down when the transport of Ag+ from the bulk of the liquid phase to the surface of the semiconductor particle became the rate-determining process. It has been demonstrated that, after the completion of silver deposition, the small metal particles on TiO2 surface enhance the efficiency of the semiconductor by a factor of 5 for the photooxidation of oxalic acid.