【作者】 占昌朝；

【导师】 钟明强；

【作者基本信息】 浙江工业大学 ， 材料化工， 2013， 博士

【摘要】 Ti02光催化剂因其具有无毒、价廉易得、稳定性好、抗光腐蚀等优点,已被广泛应用于解决当代具有全球挑战性的能源再生和环境净化问题。然而,纯TiO2材料的光生电子空穴对复合几率高；另一方面,TiO2晶体较大的禁带宽度,只有波长落在紫外光区(λ<387.5nm)才能被激发,严重地阻碍了对太阳光能量(紫外光～5%,可见光～43%,红外光～52%)的有效利用。为实现其对太阳光能量的高效利用,通过掺杂、半导体复合等改性手段调控TiO2晶体带隙,将光吸收边带红移到可见光区,是具有重要应用价值的研究方向。本文通过介孔化、掺杂、负载、表面硫酸化改性等技术手段,拓展TiO2光响应范围、提高量子效率,制备了6种高活性TiO2可见光催化剂。通过TEM、XRD、XPS、BET、UV-vis、IR、TG、PL等分析表征手段对TiO2光催化剂的结构、形貌、表面化学组成、光学性能进行了表征。考察了不同元素掺杂对光催化活性的影响,研究了其在环境治理方面的应用,为Ti02可见光催化剂的开发应用提供了实验和理论依据。研究取得了如下主要创新结果：(1)通过原位溶胶-凝胶法成功地制备了一种新型紫外和可见光响应介孔SO42-/xMo-TiO2@SiO2复合光催化剂,与商业化光催化剂Degussa P25相比较,发现制得的复合光催化剂紫外和可见光催化活性显著提高。复合光催化剂具有多级介孔结构、较大的比表面积、典型的锐钛矿相,Mo已掺入到TiO2晶格。以甲基橙为模型化合物,光降解试验表明复合光催化剂的光活性依赖于Mo掺杂剂的浓度,当Mo/Ti=0.5mol%时,表现出最佳的紫外和可见光催化活性,其紫外光解60mmin及可见光催化反应40h时甲基橙脱色率分别为100%、80.2%。适量掺杂可以捕获光生电子和减少电子空穴的复合率,加快光催化反应。复合光催化剂具有良好的重复使用性能,循环使用6次后紫外光催化降解20mg/L的甲基橙溶液60min,脱色率仍然保持在90.0%以上。(2)以钛酸四丁酯为前驱体,P123为模板剂,钨酸铵为掺杂剂,通过溶胶凝胶法合成了可见光响应介孔SO42-/xW-TiO2@SiO2复合光催化剂。研究分析表明,W掺杂不仅拓展了Ti02光催化剂可激发光范围,还使之具有较大表面积及孔容、高锐钛矿相结构、高光生电子空穴分离效率。复合光催化剂的紫外与可见光催化活性均高于P25,当W/Ti=0.25mol%,光催化活性最高,其紫外光解60min及可见光催化反应40h的甲基橙脱色率分别为98.89%、91.7%,使用5次后紫外光解60min甲基橙脱色率仍然保持在94.6%。(3)成功制备了纯锐钛矿晶相的SO42-/xRE(Nd3+, La3+, Y3+)-TiO2@SiO2复合光催化剂。稀土离子掺杂复合光催化剂不仅抑制了晶粒生长,还阻止了锐钛矿相向金红石相的转变。最适宜掺杂浓度为0.25mol%, SO4270.25mol%RE (Nd3+, La3+, Y3+)-TiO2@SiO2光催化剂产生了较强的可见光吸收,带隙变窄。介孔SO42-/0.25mol%Nd-TiO2@SiO2光催化剂的光催化活性最好,其紫外与可见光催化活性均高于P25,紫外光下60min甲基橙脱色率为99.8%,可见光下40h甲基橙脱色率为90.5%,经循环使用6次后紫外光解120min后,甲基橙脱色率为95.8%。这种高活性是因为稀土离子掺杂光催化剂具有大的比表面积、良好的结晶性、光吸收红移现象及高光生电子空穴分离效率。(4)以钛酸四丁酯为钛源、P123为模板剂、氯化铌为掺杂剂,通过微波辅助溶胶-凝胶法合成了可见光响应介孔SO42-/xNb-TiO2@SiO2复合光催化剂。微波辅助制备的介孑(?)SO42-/xNb-TiO2@SiO2复合光催化剂不仅拓展了光吸收范围,还使之具有较大比表面积、孔体积、典型的锐钛矿结构、高光生电子空穴分离效率。其中微波加热法制备的介孑(?)SO42-/0.25mol%Nb-TiO2@SiO2复合光催化剂的紫外与可见光催化活性最高,均高于商业化光催化剂P25,紫外光照60min,甲基橙脱色率为99.28%；可见光照40h,甲基橙脱色率为84.43%,循环使用5次后紫外光解脱色率仍保持在93.6%。更多还原

【Abstract】 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.更多还原