| Nonmetal doped nano-TiO2 photocatalysts, which have visible photocatalytic activity, were prepared by using a sol-gel method and a hydrothermal process in the paper. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS) and X-ray photoelectron spectroscopy (XPS). Their photocatalytic activities were investigated on degradation of dyes. The experimental results were as following:(1) The photodegradation experimental conditions of Alizatin Green (AG) were optimized in the paper. The AG dye contained nano-TiO2 was irradiated with 300 W high-pressure mercury lamp in the SGY-I photocatalytic reactor. The experimental factors, which may affect the photodegradation, such as the initial pH value of solution, the amount of nano-TiO2, dyestuff concentration and the different Oxidizer on the degradation percentage for AG were discussed. It indicated that the degradation ratio decreased rapidly with increasing of AG concentration. After 30 min the maximal degradation rate was about 92.3% when the amount of TiO2 is 2.0 g/L and the initial pH value is about 5.0. The degradation of AG increased 10.2%, when H2O2 was added into the dye.(2) Series of nitrogen doped TiO2 catalysts were prepared by using the sol-gel method. The influences on the crystalline phase, morphology and photocatalystic activities of N-TiO2 were studied with the experimental condition of various ratio of N/Ti in reaction, baking temperature and various nitrogen sources. The notable red shift of the absorption edge of samples was observed compared with that of P25.(3) The N-doped anatase TiO2 nanoparticles were prepared by the hydrothermal process with further calcination treatment. The phase composition, microstructure and morphology of the samples changed significantly depending on pH values, different amines, and calcined temperatures. The average crystallite size of the anatase samples was ca. 20 nm. There were excellent photocatalytic activities under irradiation due to the absorption edge shift toward lower energies. The incorporation of nitrogen impurities in the anatase TiO2 was studied by ATK based on first-principles calculations. The calculated electronic band structures for substitutional and interstitial N-doped TiO2 indicated the formation of localized states in the band gap, which could account for the experimental results that the samples had visible light response.(4) The N-doped, S-doped and N, S-codoped TiO2 nano- crystals were prepared by the sol-gel method using dodecylamine as nitrogen source and thio urea as sulphur source. The properties of the obtained photocatalysts were characterized by XRD, TEM, DRS, and XPS respectively. Photocatalytic activities of the anatase products were investigated on the degradation of methyl orange (MO). First principles calculations of castep have been carried out based on density-functional theory (DFT) for anatase TiO2 system. The electronic structure, including the energy band structure and Density of States (DOS), was discussed in order to explain photocatalytic performance of the products. The electronic structure was modified by introducing localized states in the band gap due to the incorporation of doping element. Due to the impurity states, the electron transiton from the valence band to the conduction band under irradiation became easier. It accounted for the photocatalystic activities in the visible region.It could be concluded from the experimental and the theoretical results that both N and S were beneficial to increase photocatalystic activity and improve photo-response in the visible light region. It indicited that multi-component co-doped would be a potential and effective technique to improve the optical property of TiO2.
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