| Titanium dioxide (TiO2) has been considered as one of the most promising materials for its application in photocatalysis and photoelectric conversion because of its high chemical stability, corrosion resistance, non-toxicity and low cost etc. However, the wide band gap (3.0-3.2eV, only absorbing the UV light ofλ< 387nm) and the easy recombination of photoinduced electrons and holes result in a low efficiency of photocatalysis and seriously limit the practical application of TiO2. In order to improve the photocatalytic activity or extend the optical absorption to the visible light region, in this dissertation, the two method was developed to prepare the C-TiO2-MMT, V-TiO2-MMT, C-V-TiO2-MMT (a sol-gel method), to prepare TiO2 catalysts adding of surfactants by the hydro-thermal method. The chemical composition and structural properties of these catalysts were investigated by XRD, TEM, XPS, FT-IR, Nitrogen adsorption isotherms and UV-Vis spectroscopy, and their photocatalytic activity were studied in detail.(1) A series of TiO2-montmorillonite (MMT) photocatalysts doped with vanadium and/or carbon were successfully synthesized by a sol-gel method and their structural properties and catalytic characteristics were studied. The results showed that a small amount of MMT is highly dispersed in the TiO2 system which can cause the layer silicate of MMT to behave as barriers of preventing TiO2 powders from agglomeration and natural crystallization. On the one hand, the average particle sizes of MMT-containing catalysts were smaller than those of the catalysts without MMT; one the other hand, some metal ions on MMT offer rich vacant d-orbits. These factors had different effects on the photo-catalytic activities. C-TiO2 and V-TiO2-MMT had higher activities under UV-Vis irradiation. The photo-catalytic activity of C-TiO2 was the highest because the elemental carbon acted as a photo-sensitizer.(2) A series of Ti/MMT nanocomposites doped with V4+which has different ratio of Ti/MMT were successfully prepared by a sol-gel process. The different Ti/MMT ratios exerted a great influence on the microstructures of the catalysts and their photocatalytic activities. Moreover, we also investigated that the effect of different washing media on the pore size and the volume of the catalysts and photo degradation efficiencies of dye. The results showed the special layers of MMT can behave as barriers to prevent powders from agglomeration. the high activity of V-TiO2-MMT/120 nanocomposites can be due to its smaller particle size, its relatively larger surface area and the red shift of the onset absorption edge in the UV-Visible DRS. However, the high activity of V-TiO2-MMT/30 can be ascribed to the significant photo-absorption in the visible light region and Ti active sites of the partial pillared nanocomposites which are easier to touch with dye and lead to a higher degradation rate; the photocatalytic activity of the catalysts washed by ethanol is the highest.(3) Under effects of two different surfactants (Polyvinyl accohol-400, water-soluble; Linoleic acid, water-insoluble), the nano-TiO2 photocatalysts were prepared by the hydro-thermal method. The results showed that the TiO2 catalysts prepared with modifying linoletic acid had relatively the low BET specific surface areas, the uneven distribution of particles, the no special grain shapes, and the weak photocatalytic activities under visible light; but the TiO2 modifying polyethylene glycol-400 showed some excellent effects, including the large BET specific surface areas, the high distribution of particles, and various special grain shapes (such as square, diamond, hexagonal, bullet type, etc). Simultaneously, the two catalysts which were P-TiO2-5/10 and P-TiO2-8/10 had relatively high photocatalytic activities. |
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