Studies On The Preparation And Photocatalytic Activities Of Micro-nano TiO₂-based Composite Visible Light Photocatalysts

Semiconductor TiO2 has a broad application potential in the fields of energy, environmental protection and materials due to low cost, non-toxicity, high photocatalytic efficiency and physicochemical stability. Because of the wide band gap of TiO2, it only has ultraviolet photocatalytic activity, limiting its use of sunlight. In previous reports, the methods of improving the photocatalytic activity of TiO2 mainly include morphology controlling, element doping, metal modification, coupling semiconductor, etc. In the thesis, the micro-nano materials of flower-like and sheet-like TiO2 with different morphologies and surface areas were prepared via hydrothermal route. Second, non-metallic elements N, F and rare earth element Er were doped in TiO2, and the materials doped with N and F elements have effect on the morphology of TiO2. (NH4)Er5F17/TiO2 composite photocatalysts were obtained and show the visible light response because of the f electronic transition of rare earth element Er in visible range, their best composite ratio and possible catalytic mechanism were explored. Thirdly, conducting polymer polyaniline were used to combine with different morphologies TiO2 and the best composite ratio and photocatalytic mechanism were explored. The reserch results are as follows:(1)The flower-like and sheet-like TiO2 materials with larger specific surface areas were obtained via hydrothermal route at 160?180? and calcination using tetrabutyl titanate and titanium powder as titanium source, glacial acetic acid or hydrofluoric acid as solvent. They have more efficient degradation activity than P25 under UV irradiation, but the TiO2 materials with larger grains and more perfect crystallinity are not as high as P25. In the process of preparation of flower-like TiO2, NH4F was added to prepare N, F doped TiO2 material. Doping N, F elements not only influences the photocatalytic activity, but also changes its morphology.(2)A series of different mass ratios of (NH4)2ErsF17/TiO2 composite photocatalysts were prepared through one step hydrothermal route and they were named as ET-0.02,ET-0.04,ET-0.01and ET-0 respectively, according to n(Er)/n(Ti) mole ratio. The research results show that the photocatalytic efficiency for degrading Rhodamine B is ET-0.02>ET-0.04>ET-0.01>ET-0>P25, when n(Er)/n(Ti)=0.02, it has the highest photocatalytic activity of RhB degradation because of its uniform dispersion, stronger light absorption and the lower electron-hole recombination rate.