(291c) N Doped TiO2 for Photocatalytic Oxidation of CO in Visible Region Synthesized By Novel One Step Liquid Flame Spray Pyrolysis (LFSP): Kinetics and Mechanism

The effects of nano sized N doped TiO₂ catalyst on the visible light photocatalytic oxidation of gaseous CO were investigated. A series of N-TiO₂ catalyst of nanosized crystals with high monodispersity and dimensional homogeneity are synthesized by using the novel single step Liquid Spray pyrolysis (LFSP) method. In order to improve the visible light response and to further narrow the band bap of TiO₂ catalyst, nitrogen is used as the dopant in this method. Different quantities of N 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 nitrogen doping concentration could reach to 1.31 wt% owing to the homogeneous doping in the mesoporous TiO₂ catalysts. The nitrogen 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 photoconversion of CO to CO₂ is quantitative in the presence of O₂. The photocatalytic CO oxidation rates and the amounts of N 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 H₂O. The addition of water vapor dose not affects significantly the CO photooxidation kinetics in the presence of O₂. The main oxidants in CO Photocatalytic oxidation seem to be produced from adsorbed O₂. The photocatalytic oxidation kinetics was investigated in detail as a function of N loading, coated TiO₂ mass, CO concentration, O₂ concentration, light intensity, additives, and humidity. These interesting results will be discussed in the presentation.