| TiO2 hasbroad prospect in environmental protection material because of its high photocatalytic activity, good chemical stability, and other advantages. But as a result of band gap of TiO2 (about 3.2 eV) and can only absorb less than 387 nm wavelength UV-light, and UV-light accounts for only about 4% of the total solar radiation energy, visible light accounts for about 40% of the total solar radiation energy, the visible light can’t beutilized effectively; While TiO2’s photo-quantum efficiency is very low due to its high recombination rate between photo-generated electrons and holes.These factors seriously limits the application of TiO2, thereforelt’s neccessary touse effective methods to get visible light response and efficient TiO2 photocatalyst. There are many methods which can improve the photocatalytic activity of TiO2 such as ion doping, noble metal loading, and semiconductor compound, dye sensitization and so on. Among them, ion doping is considered to be the most effective modification method.In this thesis, under the guidance of the theoretical calculation by our group, S-Y-TiO2 and S-B-TiO2 samples were prepared by sol-gel and hydrothermalmethod,S-Ag-TiO2 samples were prepared by sol-gel process, respectively.AH the samples were characterized by X-ray diffraction(XRD), fourler transform-infrared spectrometer(FT-IR), ultraviolet-visible diffuse reflection spectrum(UV-Vis), photoluminescence(PL) and so on.The photocatalytic activity of samples was evaluated by the degradation rate of methylene-blue (MB) under under 30 w fluorescent lamp irradiation.The details of work are as the follows:1. S/Y co-doped TiO2 (S-Y-TiO2) photocatalystsS-Y-TiO2 samples were synthesized by sol-hydrothermal process in which distilled water as the solvent, Ti(OC4H9)4 as Ti source, SC(NH2)2 as S source, Y(NO3)3·6H2O as Y source. The influences of S doping concentration, Y doping concentration and heat treatment temperature on the properties of S-Y-TiO2 were researched.The results show that the S/Y co-doped inhibited the grain growth and phase transition of TiO2,reduced the recombination rate of photo-generated carriers and broaden the light absorption spectrum to visible light region, and enhanced the photocatalytic activity of TiO2.The best preparation conditions are:heat treated at 500℃,S doping concentration:S:Ti= 1: 20(mole ratio), Y:Ti= 0.6%(mole ratio).Under thispreparation condition, the degradation rate of methylene blue(MB)was 90.58% after 5 h, compared with P25 (60.76%) under 30 w fluorescent lamp irradiation after 5 h, the efficiency of photocatalytic degradation of improved significantly.2. S/B co-doped TiO2 (S-B-TiO2) photocatalystsS-B-TiO2 samples were synthesized by sol-hydrothermal process in which distilled water as the solvent, Ti(OC4H9)4 as Ti source, SC(NH2)2 as S source, H3BO3 as B source. The influences of S doping concentration, B doping concentration and heat treatment temperature on the properties of S-B-TiO2 were researched.The results show that the S/B co-doped inhibited the grain growth and phase transition of TiO2, reduced the recombination rate of photo-generated carriers and broaden the light absorption spectrum to visible light region, and enhanced the photocatalytic activity of TiO2. The best preparation conditions are:heat treated at 450℃, S doping concentration:S:Ti= 1: 50 (mole ratio), B:Ti= 1:25(mole ratio). Under this preparation condition, degradation rate of MB was 91.31% after 5 h, compared with P25 (60.76%) under the same test condition, the efficiency of photocatalytic degradation of MB improved significantly.3. S/Ag co-doped TiO2 (S-Ag-TiO2) photocatalystsS-Ag-TiO2 samples were synthesized by sol-gel process in which distilled water as the solvent, Ti(OC4H9)4 as Ti source, SC(NH2)2 as S source, AgNO3 as Ag source. The influences of Ag doping concentration and different ion doping on the properties of S-Ag-TiO2 were researched. The results show that the S/Ag co-doped inhibited the grain growth and phase transition of TiO2, broaden the light absorption spectrum to visible light region, reduced the recombination rate of photo-generated electron and hole pairs,and enhanced the photocatalytic activity of TiO2.When heat treated at 500℃, doping concentration S:Ti=1:50(mole ratio), Ag:Ti=0.025%(mole ratio), the degradation rate of MB was 72.21%, higher than that of Pure TiO2(47.05%) under the same experimental conditions.The main innovations of the thesis are mainly focused on the following aspects:(1)The research work of this thesis is carried out on the basis of theoretical calculation by our group, which can effectively overcome the blindness and repeatability of the research, meanwhile, the theoretical calculation results can give theory support and explanation tothe experiment phenomenon and mechanism analysis, so as to achieve theory combined with practice;(2)The research about rare earth elements with nonmetallic elements co-doped nano-TiO2is relatively few at home and abroad, and there is no on element Y and S co-doped TiO2 photocatalyst seems to beseldom investigated and reported. |
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