Photocatalytic Performance Of Doped TiO₂ Thin Films Prepared By Sol-gel

Semiconductor photocatalytic technology has a very broad application prospects in environmental governance and the conversion of solar energy. In these semiconductor materials, TiO2 has been attracting much attention owing to its chemical stability, non-toxic, low cost and light corrosion resistance. However, TiO2 can only absorb the ultraviolet part of sunlight due to its wide bandgap, and the electrons and holes can easily combine, resulting in low photocatalytic activity of TiO2. Therefore, development of TiO2 photocatalysts activated by both UV light and visible light and improvement of TiO2 photocatalytic quantum efficiency are the direction of researchers'efforts.The purpose of this thesis is to improve the scope of the absorptiom and photocatalytic efficiency. TiO2 thin films were prepared by dip sol-gel on glass substrates and transition metal ions, such as:Cr, Fe, Cu, are dope in to modify the TiO2 thin films. Undoped and doped TiO2 thin films were characteristic using AFM, UV-vis, FL, XPS and XRD.The stability of the sol depends on pH, mixed with water quantity, alcohol content. Film crystalline phase is anatase at lower temperatures, and convert into rutile at higher annealing temperature. The critical conversion temperature for doped film is much lower than that of undoped TiO2 film, indicating that ion doping facilitate the phase conversion from anatase to rutile phase.The results show that:on the one hand, the pH, mixed with water quantity, alcohol content are important influence on the sol stability; on the other hand, as the annealing temperature, the film crystal structure from anatase to rutile transformation and the crystal phase transition temperature lower as ion doped; and then, the doping ion species, doping concentration and annealing temperature have great impact on the absorption spectrum and photocatalytic activity of TiO2 nanometer thin film. The absorption edge red shifted 520nm,800nm and 730nm respectively, after Cu, Cr, Fe doping. They correspond to the optimal concentration are 0.2M,0.2M and 0.3M; the optimal annealing temperature are 300℃,400℃and 500℃.