(536a) S Doped TiO2 for Photocatalytic Oxidation of CO in Visible Region Synthesized By Novel One Step Liquid Flame Spray Pyrolysis (LFSP): Kinetics and Mechanism

A novel single step Liquid Spray pyrolysis (LFSP) method is used to synthesize a series of S-TiO₂ catalyst of nanosized crystals with dimensional homogeneity and high monodispersity. A series of S-TiO₂ catalyst of nanosized crystals with high monodispersity and dimensional homogeneity are synthesized by using the novel single step Liquid Spray pyrolysis (LFSP) method. Different quantities of S was incorporated into TiO₂ catalyst, which is beneficial to the generation of the successive energy bands inside the TiO₂ band gap. Our XPS results indicate that the S doping concentration could reach to 8 wt% owing to the homogeneous doping in the mesoporous TiO₂ catalysts. The S doped TiO₂ catalyst exhibit such excellent characteristics as high specific area, relatively small particle size, pure anatase phase and excellent UV-vis absorption capacity in the range of 400-800 nm, which are all beneficial to the photocatalytic oxidation of CO under the visible light irradiation. The photo conversion of CO to CO₂ is quantitative in the presence of O₂. The photocatalytic CO oxidation rates and the amounts of S deposited on TiO₂ surface show a close correlation. The CO photooxidation is strongly inhibited in the absence of O₂ or in the presence of alternative oxidants such as N₂O and H₂O. The addition of water vapor little affects the CO photooxidation kinetics in the presence of O₂. Hydroxyl radicals do not seem to play a significant role in CO photooxidation on S-TiO2. The photocatalytic oxidation kinetics was investigated in detail as a function of S loading, coated TiO₂ mass, CO concentration, O₂ concentration, light intensity, additives, and humidity.