Enhanced photocatalytic activities of titanium dioxide and its solid solutions

In this thesis, Ti_1−xM_xO₂ (M = transition metal) solid solution were successfully synthesized by citric complexing method, and for the first time, used as photocatalyst in this research area. The solid solutions Ti_1−xM_xO₂ (M = V, Zr and Sn) have been shown to have higher photocatalytic activities for the degradation of volatile organic compounds as compared to their counterparts TiO₂. Based on the characterization results of XRD, XPS, UV-vis diffuse reflectance spectra, transition adsorption decay spectra and zeta potential measurements on these solid solutions, it was found that the photocatalytic activity of these solid solutions is a function of these metal substitution level and related to some changes in band gap, lattice defects and surface acidity resulting from M substitution for Ti in TiO₂ lattice. In addition, we investigated the relationship between oxygen adsorption and photo-catalytic activity of thermally treated TiO₂, and measured the photo-catalytic activity of TiO₂ thermally treated at different temperatures in air and in vacuum. By combination of the results of polycrystalline X-ray diffraction, ESR (electron spin resonance) spectra, adsorption oxygen and BET surface area measurements, a new acceptable explanation for that the photo-catalytic activity of TiO₂ was increased after thermal treatment in air is offered.