The enhancement of photodegradation efficiency using Pt-TiO2 catalyst.

This study investigates the mechanism of photosensitization and the recombination of excited electron-hole pairs affected by depositing platinum (Pt) on the surface of titanium dioxide (TiO2). A new catalyst of Pt-TiO2 was prepared by a photoreduction process. Being model reactions, the photocatalytic oxidation of methylene blue (MB) and methyl orange (MO) in aqueous solutions using the Pt-TiO2 catalyst was carried out under either UV or visible light irradiation. The experimental results indicate that an optimal content of 0.75%Pt-TiO2 achieves the best photocatalytic performance of MB and MO degradation and that the Pt-TiO2 catalyst can be sensitized by visible light. The interaction of Pt and TiO2 was investigated by means of UV-Vis absorption spectra, photoluminescence emission spectra, and X-ray photoelectron emission spectroscopy. The Pt0, Pt2+ and Pt4+ species existing on the surface of Pt-TiO2, and the Ti3+ species existing in its lattice may form a defect energy level. The Pt impurities, including Pt, Pt(OH)2, and PtO2, and the defect energy level absorb visible light more efficiently in comparison with the pure TiO2 and hinder the recombination rate of excited electron-hole pairs.