| Titanium dioxide photocatalyst is widely used to solve the energy regeneration and environmental purification problems as contemporary global challenges due to it has many advantages such as non-toxic, cheap availability, excellent stability, against photo-corrosion, etc. However, the recombination rate of photoinduced electron-hole pairs is particularly high in the bulk TiO2photocatalysts. On the other hand, TiO2with wide band gap energy excited only in the ultraviolet light (UV) region (λ<387.5nm) is seriously inhibits the fully using of natural sunlight, which consists of5%ultraviolet light,43%visible light, and52%infrared light. In order to achieve effective utilization of solar energy, regulating band gap energy of TiO2crystalline by modification techniques such as doping, semiconductor coupling and shifting its absorption edge from UV region to the visible light (VL) region is research direction with important application value.In order to expend light responsive region and enhance quantum efficiency of TiO2, six kinds of high photoactivity samples have been prepared by mesopore, doping, support and surface modification etc., whose structure, morphology, surface chemical components and optical properties were characterized by varoius techniques. The effect of different elements doping on photocatalytic activity and application of samples in environmental governance have been studied, which provides a solid experimental foundation and theoretical basis for developing the application of VL photocatalyst. Some innovative results obtained are as follows:1. A novel UV and VL responsive sulfated Mo-doped TiO2@SiO2mesoporous photocatalyst was successfully in situ synthesized by a sol-gel method. Moreover, both UV and VL photocatalytic activity of this composite photocatalyst was greatly enhanced comparing with Degussa P25. Their multi-level mesoporous structure, high specific surface area and typical anatase phase were demonstrated by varoius techniques. The VL absorption and doping Mo into TiO2matrix were confirmed as well. It was founded that the photocatalytic activity of methyl orange (MO) degradation depended on the concentration of the Mo dopant. A0.5mol%Mo dosage was optimal for both UV and VL photoactivity. The suitable amount dopants can capture photogenerated electrons and decrease the recombination rate of electron-hole pairs and accelerate photocatalytic reaction. Furthermore, the composite showed good recycling endurance, the decolorization rate of MO with initial concentration of20mg/L still keeps at above90.0%under UV irradiation for60min after six consecutive cycles.2. VL driven mesoporous sulfated W doped TiO2@fumed SiO2photocatalysts were synthesized via sol-gel method with tetrabutyl titanate (TBOT) as precursor, P123as a template and ammonium tungstate as dopant. The results confirmed by varoius techniques showed that the doping of W resulted in not only an increase in the surface area, pore volume and separation efficiency of photogenerated electron-hole pairs of sulfated mesoporous TiO2@SiO2, but also in inhibition of phase transition from anatase to rutile. Photo-degradation results revealed that W doping could greatly improve the photocatalytic activity of sulfated TiO2@SiO2with mesostructure, higher than that of undoped samples and the commercially available Degussa P25titanium dioxide by degradation of methyl orange aqueous solutions. Doping with W showed higher photocatalytic activity and its optimal molar dosage was0.25%, which caused MO discoloration rate of91.7%,98.9%irradiation under VL (λ>400nm) for40hours and UV for60min respectively. The decolorization rate of MO is up to94.6%under UV irradiation for60min after five consecutive cycles.3. A novel processing technology was developed for the preparation of high photoactive sulfated RE-doped TiO2@fumed SiO2composite photocatalyst with mesoporous and anatase single-phase structures. Doping of RE ions not only suppressed the crystal growth, but also prevented phase transition from anatase to rutile phase. The optimal molar dosage was0.25%, The SO42-/0.25mol%RE (Nd3+, La3+, Y3+)-TiO2@SiO2showed strong absorption in the UV-vis range and a red shift in the band gap transition, narrowing the band gap. Photocatalytic efficiency of SO42-/0.25mol%Nd-TiO2@SiO2sample exhibits higher than samples doping with the other two RE ions and commercial P25, which caused99.8%,90.05%MO to be degraded under UV and VL irradiation, respectively. The decolorization efficiency of MO keeps at95.8%under UV irradiation for120min after six consecutive cycles. The enhanced photocatalytic activity could be attributed to the higher specific area, good crystallinity, strong VL absorption, the effective separation of photogenerated electron-hole pairs in the RE ions doping photocatalyst.4. VL responsive mesoporous SO42-/xNb-TiO2@SiO2photocatalysts were prepared by microwave assited so-gel method with TBOT as the precuesor, P123as a template and niobium chloride as dopant. Microwave assisted sol-gel method fabrication not only extend light absorption region, but also obtain an increase in the surface area, pore volume, typical anatase structure, high separation efficiency of photogenerated electron-hole pairs of mesoporous SO42-/xNb-TiO2@SiO2photocatalyst. Mesoporous SO42-/0.25mol%Nb-TiO2@SiO2displays the highest UV and VL photocatalytic activity among all photocatalysts including Degussa P25, which photodecolorization rate of methyl orange were84.43%,99.28%irradiation under VL (λ>400nm) for40hours and UV for60min, respectively. Mesoporous SO42-/0.25mol%Nb-TiO2@SiO2also showed good recycling endurance, the photocataiytic decolorization rate for MO still reaches93.6%after five consecutive cycles under UV irradiation for60min. |
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