Doping Modified Tio <sub> 2 </ Sub> Photocatalyst Activity,

The photocatalytic oxidation technique of TiO₂ has been paid more and more attention for many advantages, such as less energy cost, mild reaction condition, easy operation and less secondary pollution. However, TiO₂ may show photocatalytic activity only under irradiation of ultraviolet (UV) light for its wide band gap (Eg³.2eV), most of the sun light is underutilized. Furthermore, easy recombination of photo-induced electrons and holes makes the efficiency of photoquantum low. Those unfavorable factors have the photocatalytic oxidation technique of TiO₂ limited in practice.Considering the problems above, the idea of TiO₂ photocatalysts by doping modification was presented. Pure TiO₂, Ce-doped, I-doped and I/F codoped TiO₂ photocatalysts were prepared by sol-gel method. The microstructures of prepared photocatalysts were characterized by XRD, TEM, XPS and UV-Vis analysis. The effect of calcining temperature and content of dopants on the photocatalytic activity was studied by decomposing methylene blue. Recycle of photocatalysts was also discussed in this paper.The study showed that the doping modification not only prevented the phase transformation process of Ce-doped, I-doped and I/F codoped TiO₂ photocatalysts from anatase to rutile, but also suppressed crystal growing. Compared to pure TiO₂, those three TiO₂ photocatalysts revealed stronger absorption and blue shift in the UV light region, and the responding area to sunlight was enlarged to visible light area.The results of photocatalytic degradation for methylene blue(10mg/L) indicated that photocatalytic activity of 0.05%Ce-TiO₂ and 10%I-TiO₂ calcined at 500℃ was the highest among the Ce-TiO₂ and I-TiO₂. The photodegration rate reached 73% and 82.3% in 4h, respectively. Photocatalytic activity of I/F-TiO₂ also improved obviously, 97.4% of methylene blue was photodegraded after 2h of irradiation. Besides, it was found that methylene blue mineralized eventually into NH₄⁺, NO₃^- and SO₄^2-, respectively.