【作者】 赵永勋；

【导师】 杨碚芳；

【作者基本信息】 中国科学技术大学 ， 材料物理与化学， 2011， 硕士

【摘要】 近年来随着工业的发展导致的环境污染和能源短缺问题日愈严重,借助半导体的光催化作用,进行有害有毒污染物的光催化降解及光催化合成引起了广泛关注。其中TiO₂由于资源丰富,价格低廉,无毒环境友好,较高的化学稳定性以及易掺杂改性等优点,被认为是理想的光催化材料得到深入研究。但是,TiO₂的光催化能力主要体现在波长小于380 nm的紫外光照射下,加上光生电荷容易复合导致量子产率低大大限制了它的实际应用。所以对TiO₂进行改性,提高光催化效率尤其关键。对TiO₂改性主要有两个方面:一是化学改性,包括金属和非金属掺杂、贵金属沉积以及与具有匹配能带结构的半导体进行复合;二是物理改性,如制备具有独特形貌的TiO₂纳米管/棒、纳米线、纳米带、核壳结构的TiO₂复合物、微孔介孔结构的TiO₂以及与光子晶体耦合得到有序多孔结构的TiO₂反蛋白石。基于以上方法,本文将物理和化学改性结合起来制备了Ag纳米颗粒修饰的TiO₂反蛋白石光催化剂。主要工作为:1.用实验室自制的SiO₂微球,通过垂直沉降法在玻璃衬底上制备出蛋白石胶体晶体模板;2.溶胶凝胶浸渍提拉法将TiCl₄溶胶填入SiO₂模板,热处理使填充物凝胶化,并高温煅烧使TiO₂结晶,热氢氧化钠溶液去除模板后,得到有序多孔结构的TiO₂反蛋白石;3.利用简单的湿化学方法,在TiO₂反蛋白石上沉积平均尺寸10 nm左右的Ag纳米颗粒;4.通过X射线衍射、拉曼光谱、场发射扫描电镜、高分辨透射电镜、光电子能谱、紫外可见吸收谱和光致发光谱的表征对样品的物相组成、表面形貌和微结构、元素组成和价态、光学性质等进行了研究;5.降解亚甲基蓝水溶液的实验证明,合成的催化剂具有较高的光催化活性和稳定性,尤其是可见光催化活性有较大幅度的提高。AgNO₃前驱体溶液浓度为10 mM时,TiO₂反蛋白石可见光催化效率最高,反应速率常数是相同Ag负载量TiO₂无序膜的4.20倍。催化活性的提高,归因于Ag纳米颗粒表面等离子体吸收和反蛋白石有序多孔结构多重散射效应的协同作用。更多还原

【Abstract】 Recently, the problems of environment pollution and energy shortage become more and more serious with the development of industry. Photocatalytic degradation of harmful toxic pollutants and photocatalytic synthesis using semiconductor photocatalysts have induced extensive attention. Among all these candidates, TiO₂ has been considered the ideal photocatalytic materials and obtained deeply studies. Since TiO₂ are resource-rich, cheap, non-toxic, chemical stability and easy to dopant. However, the photocatalytic activity of TiO₂ was reflected under the ultraviolet light with wavelength shorter than 380 nm. Furthermore, the practical application of TiO₂ was greatly restricted by its lower quantum yield, which comes from the recombination of photogenerated charges. Thus, it is mostly important to modify TiO₂.There are mainly two methods for TiO₂ modification. The one is chemical modification, including metal and nonmetal doping, noble metal deposition and compositing with other semiconductors. The other is physical modification, such as preparation TiO₂ nanotubes/rods, TiO₂ nanowires, TiO₂ nanobelts, TiO₂ composition which has core-shell structure, micro/mesoporous TiO₂ and coupled with photonic crystals gotten ordered porous TiO₂ inverse opals. Based the above ways, we combined physical and chemical modification and fabricated Ag nanoparticles decorated TiO₂ inverse opals. The main works are as following:1. Colloidal crystal templates were prepared on the glass substrates using SiO₂ microspheres via vertical sedimentation.2. SiO₂ templates were filled with TiCl₄ sol through sol-gel dip-coating. Gelation of fillers was by heat treatment, then TiO₂ crystallization by high temperature calcining. The removal of templates was using hot NaOH solution and achieved ordered porous TiO₂ inverse opals finally.3. Ag nanoparticles with average size about 10 nm were deposited on TiO₂ inverse opals by a facile wet chemical route.4. Crystal phase, surface morphology and microstructure, the elemental composition and chemical state,optical properties were investigated by X-ray diffraction （XRD）, Raman spectroscopy, field-emission scanning electron microscopy （FESEM）, high-resolution transmission electron microscopy （HRTEM）, X-ray photoelectron spectroscopy （XPS）,UV-vis absorption spectra, and photoluminescence spectroscopy （PL）. 5. The experiments of methylene blue degradation confirmed that the result catalysts have enhanced photocatalytic activities and stability, especially the visible-light photocatalysis. Furthermore, the remarkable improvement in methylene blue degradation was appearing on TiO₂ inverse opal with optimizing AgNO₃ concentration 10 mM in the precursor solution, which exhibited 4.20 times visible-light reaction rate constant comparing with conventional Ag loaded TiO₂ film without ordered porous structure. This obvious enhanced visible-light photocatalytic activity can be attributed to the synergetic effect of Ag nanoparticles surface plasmon absorption and the multiple scattering effect of inverse opal ordered porous structures.更多还原