| Environment pollution and energy resource crisis are the hot topics today and, effective utilization of solar energy to solve pollution problems attains much attention now. With outstandingly characteristics in widely utilization of solar energy, low energy consumption, moderate reaction condition, convenient operation, no secondary pollution, and good oxidation degradation for bio-refractory organic pollutants, the semiconductor oxide heterogeneous photocatalytic technology is a hot research topic in environment science. Among those semiconductor oxides, TiO2 has excellent photoelectric properties, which can activate photoelectron, occuring redox reaction on surface, decomposing most organic pollutants and mineralizing them into CO2, H2O and other small inorganic molecules completely under light irradiation. TiO2 is also chemical stable, safe and imnoxious, abundant source. However, the energy band-gap of TiO2 in the anatase crystalline is wide (Eg≈3.2eV) and it can only catalyze the degradation of persistent organic pollutants under ultraviolet light (300nm～400nm) irradiation, which accounts for only a small part (3%～5%) of solar energy with low quantun yield. The present work is focused on preparation of doped TiO2 to get good photocatalytic performance catalyst.In this dissertation, the basic principle about semiconductor photocatalysis was reviewed briefly at first. The methods, research progress and main problems about improving the total quantum-efficiency and utilization effeiciency of solar energy for semiconductor photocatalysis have been summarized. Then, the more available and cheaper inorganic TiCl4 was used as raw material, and thiourea was used as the precipitator, as well as supply sulfur, S-doped nanosize TiO2 precursors were prepared by homogeneous precipitation via microwave irradiation. And then N, S-codoped nanosize TiO2 were prepared with temperature-programmed calcinations in NH3/N2 atmosphere. With the indexes of the average grain size, crystal composition, and photo catalytic activity of nanosize TiO2, the initial TiCl4 concentration, microwave power, microwave reaction time, microwave reaction temperature and calcinations temperature in NH3/N2 atmosphere on photocatalyst were studied. And process parameters were optimized also. The results showed N, S-codoped nanosize TiO2 photocatalytic activity is upmost under the follow conditions: initial TiCl4 concentration, 0.9 mol·L-1; microwave power, 900W; microwave reaction time, 0.5h; microwave reaction temperature, 95℃; calcinations temperature in NH3/N2 atmosphere, 500℃.The crystal structure and properties of N, S-codoped nanosize TiO2 were characterized by XRD, UV-Vis/DRS, FT-IR, XPS and TEM. The results showed that the catalyst has mixed phase structure of anatase and rutile. The nanoparticle were spherical or spherical-like, and the particle size in the range of 15～20nm; Nitrogen was existed in two doping states: one is substitutional N impurity, which formated joint of Ti-N-Ti doping state, another is interstitial impurity by chemical-adsorption of NH3 or NH4+; Sulfur ions (S6+) substituted partially for the lattice titanium ions (Ti4+), which resulted in the localized crystal deformation of TiO2 and the bandgap between valence band and conduction band narrowed. Visible-light photocatalytic activity obtained by N, S-codoped nanosize TiO2, was because of formation of a new impurity level, which led it's absorption spectrum red-shft to 500～550nm.N, S-codoped nanosize TiO2 has higher photocatalytic activity, and the degradation of MO in visible-light irradiation was proved fitted the pesudo-first-order model. The higher photocatalytic activity also attributed to the synergetic of N, S-codoped.Besides, the crystal phase composition of photocatalysts were effected by ionic liquid addition, and it could also assisted to nitrogen and sulfur doping. Ionic liquid with anion of [BF4]- could cause F-doping which F- absorbed on N, S-codoped nanosize TiO2. The degradation of MO showed that the visible-light activity was improved by adding ionic liquid. The mechanism of visible-light improved with ionic liquid addition has been also discussed in the wnd.
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