Synthesis And Photocatalytic Properties Of New Type Of Tio <sub> 2 </ Sub>

In recent years, much attention has been paid for heterogeneous photocatalysis owing to its potential application in many areas, especially the treatment of environmental pollutants. Among semiconductor photocatalysts, TiO2 is most frequently employed because of its non-toxity, low cost, high activity and strong stability in aqueous media. Mesoporous TiO2 as photocatalyst to deal with the environmental pollutants is one of the investigative hotspot. First, high surface area of mesoporous TiO2 improves the touch probability between pollutants and catalysts, and mesopores make the products and reactants have higher diffuse rate in the multiphase catalysis reaction; On the other hand, rich hydroxyl on the surface can enhance the ability of TiO2 to adsorb water. The hydroxyl and water can yield hydroxyl free radical which react with positive hole and hydroxyl free radical is the powerful oxidant and increase the photocatalyst efficiency. However, the shortage of the mesoporous TiO2 is the ordered mesoporous structure can be badly destroyed in the crystalline process and TiO2 can only absorb the light less than 380 nm.In order to solve these problems in mesoporous titania photocatalyst, modification with doping agents can stabilize the structure of mesoporous TiO2, and improve its quantum efficiency and photoactivity in the visible light area. Besides, other method such as alcohol hydrolysis with surfactant free self-assembly methods are also used to prepare photocatalysts which have novel morphology and high photoactivity. The photocatalytic degradation of phenol, methylthionine chloride and bichrome in aqueous solutios are used as a probe to evaluate their photocatalytic activities. XRD, XPS, TEM, SEM, BET, PLS, RAMAN, IR, DRS of pyrodine adsorption and nitrogen-adsorption were used to characterize these photocatalysts. Their photocatalytic performances were discussed briefly from either their structural characteristics or surface electronic states. Lots of experiences were provided to further develop practical photocatalysis technique.The detail research work are listed as following:1. Preparation and photocatalytic activity of well-ordered mesoporous titania photocatalyst.According to the reported EISA method, we successfully prepared a series of well-ordered mesoporous titania photocatalyst by doping metal ions, and found different ion had different effect.(1) Doping rare earth metal ion La3+ can not only restrain the change of crystal phase in TiO2 and stabilize the structure of mesoporous TiO2, but also improve the photoactivity of photocatalyst, heat stabilization and crystallization of mesoporous TiO2 photocatalysts.(2) Doping noble metal Au, we can get complex substance of mesoporous Au/TiO2. It was found that TiO2 and Au both have very high crystallization, and Au nano-particles were well embedded in the mesoporous TiO2 wall structure to greatly improve the quantum efficiency and photocatalyst photoactivity.(3) We can get complex substance of mesoporous Bi/TiO2 by doping metal Bi. Bi2O3 can narrow the band gap of TiO2 from 3.2 eV to 2.7 eV to improve the ability of TiO2 to absorb visible light more effectively in photocatalysis process.Compared with the general TiO2, mesoporous structure TiO2 can improve the photoactivity. In the same condition, when the crystallization of TiO2 is in uniform, mesoporous TiO2 can have high surface area and avail for reactant transfer easily in the mesoporous pore. The sample which has the highly ordered mesoporous structure can have high photoactivity.2. Preparation and photocatalytic activity of core-shell structure titania photocatalyst by alcoholysis method.Structure-controlled core-shell TiO2 was synthesized by fast non-template method. The catalyst has a uniform structure and affluent surface structure. Through controlling the nucleation process, we get the core-shell micro-size TiO2 particles with good dispersity and stabilization in liquid, and get core-shell or shell structure catalysts by controlling the aging time. The structure has great influence in photocatalysis process, and the core-shell structure catalyst has the best activity due to the light can reflect between the core and shell, resulting in greatly improvement of light efficiency.