| In recent years, heterogeneous photocatalysis has made great progress in photocatalytic removal of the organic and inorganic pollutants, and has been widely recognized as a highly promising environmental purification technology. Among them, Ti-based photocatalysts received extensively attention on account of their features, i.e. chemical stability, high photocatalytic activity, degradation of organic pollutants thoroughly, and no secondary pollution. However, the drawbacks of TiO2, such as low quantum yield, narrow spectral response, and harsh immobilization conditions limit the utilization and industrialization of Ti-based photocatalysts. As an effective way to improve the quantum yield and the catalytic activity of TiO2, different elements involving precious metals, rare earth metals, transition metals, and nonmetals have been doped into TiO2nanomaterials and showed better photocatalytic performances. Nevertheless, how to better use these "superior" photocatalysts in the practical process of photocatalytic degradation, in particular, how to improve the visible-induced photoactivity and reduce the cost of visible-activated photocatalyst is still a challenge. In this thesis, on the one hand, we prepared a series of transition metal doped TiO2inverse opal using sol-gel method in allusion to fabrication of the visible-activated nanostructured Ti-based materials. These materials are capable of combining the benefits of both transition metal doping and inverse opal structures, which could enhance the visible light activated photoactivities of the materials. On the other hand, we synthesized iodine doped TiO2nanocrystallites under120℃by using block copolymer assisted sol-gel method. Crystallization, iodine doping, and the formation of mesoporous structure are simuntaneously achieved. This method possesses the advantages of mild condition, low energy consumption and no organic solvent involved, which could reduce the cost of preparing visible-activated photocatalyst. The main research contents and results are as follows:1, The monodispersed polystyrene microspheres with the average diameter of190nm and the polydispersion index of0.0529were prepared by an optimized (concentration of emulsifier, amount of initiator, stirring rate and temperature) emulsion polymerization process. In view of this, the polystyrene colloidal crystal templates were assembled by veticle deposition method. Note that the dipping process was conducted on the self-made dip-coating apparatus. Compared to the commercial product, our apparatus has two features, i.e. the slow dipping rate (lower than1.5μm/min) to meet the demand of self-assembly process, and the reduced experiment error from screw-based transmission system. The morphology of the samples exhibited typical opal structures with hexagonal arrangement. Meanwhile, the colloidal crystal model showed good quality and could be further used to prepare inverse opal materials.2, Based on the above-mentioned colloid crystal templates, TiO2inverse opal (TIO) and transition metal doped TIO were fabricated by a sol-gel method and using the nitrate of iron, zinc and chromium as doping agent. The products exhibited three-dimensionally ordered macroporous (3DOM) structure and homogeneous wall composition. The macropore diameter and frame thickness of transition metal doped TIO are dependent on different metal species doped. By using rhodanmine-B and methylene blue as the model pollutants, the experiment results of photodegradation indicated that the visible photocatalytic activities of Fe-doped TIO are superior to undoped sample. The10%Fe-doped TIO exhibited the highest efficiency, giving a degradation extent of85%under visible light irradiation for4hours. Besides, we put forward a water-solvent method to fabricate Ni doped TiO2inverse opals by using ammonium lactate titanate as Ti resource and nickel nitrite as doping agent. This water-solvent method could extend the applicable scope of sol-gel method in preparation of transition metal doped TIOs.3, Iodine doped TiO2nanocrystallites were prepared by a triblock copolymer assisted sol-gel method under low temperature conditions (120℃). The results indicated that the samples were anatase structure with the diameter of～5nm. After drying, the tiny crystallites agglomerated to nanoparicles with the diameter range of20-50nm and mesoporous structure. N2absorption experiment showed the specific surface area is approximately259m2/g, and the pore diameter is about3.6nm. The existence of iodine in the samples is in I2or (I2)n form. Compared to the prestine TiO2, the doped sample exhibited higher surface oxygen radical amounts and stronger absorption in the visible range. The evaluation of photocatalytic activity of iodine doped TiO2nanocrystallites were conducted by using rhodamine-B and2,4-DCP as model pollutants, and the results indicated that iodine doped samples possessed better performance, reusability, and stability. |
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