【作者】 吴清萍；

【导师】 李旦振；

【作者基本信息】 福州大学 ， 物理化学， 2006， 硕士

【摘要】 目前以二氧化钛为基础的可见光半导体光催化剂仍然面临光生载流子转换效率低和化学稳定性差等重大问题;如何在保持化学稳定的前提下开发高效可见光光催化剂成为近些年来光催化领域的研究焦点。本文首次利用窄禁带半导体,多孔硅（PS 2.0 eV）和锆钛酸铅（PZT 2.5 eV）,作为复合材料成功地应用在光催化领域;并以PZT/TiO₂和PS/TiO₂作为可见光光催化剂对有机污染物罗丹明B的降解为例提出了可能的反应机理。本文分别采用溶胶-凝胶法制备TiO₂胶体,水热法合成纳米级PZT粉体,化学腐蚀法制备多孔硅。PZT/TiO₂和PS/TiO₂复合半导体则采用简单的化学耦合法,并在400℃下煅烧。运用X射线粉末衍射、荧光光谱、比表面、紫外-可见漫反射光谱和透射电镜等分析手段对催化剂体相及表面结构进行详细表征。通过对半导体光催化剂的载流子寿命和羟基自由基的测定（分别采用表面瞬态光电导谱和电子顺磁共振谱）揭示了光催化氧化过程的可能途径。新型二氧化钛基复合半导体材料的光催化氧化性能通过对罗丹明B的降解来确定。透射电镜证实了多孔硅,锆钛酸铅与二氧化钛的成功复合。活性测试表明,复合半导体催化剂比单独的PZT、PS、TiO₂、P25（商品）以及文献上报道的其他光催化剂有着更加优越的可见光活性。其中PS/TO2的可见光活性至少是其他催化剂活性的5倍。在相同实验条件下,PZT/TiO₂和PS/TiO₂对罗丹明B的连续五次降解,其活性均基本保持不变。实验显示,新合成的复合半导体材料解决了催化剂的化学稳定性问题。其中,多孔硅在可见,紫外光等条件下具有的光催化活性尤其值得关注,并有可能在不久的将来超越TiO₂作为新一代可见光催化剂。表面瞬态光电导和电子顺磁共振测试表明半导体之间的异质复合提高了PZT/TiO₂和PS/TiO₂催化剂的光生载流子的分离效率,促进了表面羟基自由基的生成;并提出了可见光光催化的可能机理。总之,本研究工作利用简单的耦合方法成功地制备了新型、高效、稳定的可见光光催化剂,为进一步解决环境污染问题提供了依据。更多还原

【Abstract】 Presently, visible-light TiO₂ based photocatalysts coupled with narrow bandgap semiconductors are either unstable （CdS, CdSe, etc.） or have low conversion efficiency of photo-generated carriers. How to efficiently exploit visible light active photocatalysts for degradation of environment pollutants with chemical stability has attracted much attention in recent years. In this paper, two relative narrow bandgap semiconductor, porous silicon （PS 2.0 eV） and lead zirconate titanate （PZT 2.5 eV） have been firstly applied in photocatalytic field. Herein, PZT/TiO₂ and PS/TiO₂ composites have been prepared for the first time. Mechanisms are proposed to elucidate the high photocatalytic activity of composites during degradation of organic pollutants.Titanium dioxide （TiO₂） nanoparticles were prepared by sol-gel method. Hydrothermal method was used to synthesize nanoparticles of PZT with no Pb pollutant to our environment during preparing process. The simple chemical etching method was applied to producing PS with low cost. In this dissertation, simple coupled method was employed to prepare PZT/TiO₂ and PS/TiO₂ composites. All of composite were calcinated at 673 K and used as visible-light photocatalysts in the experiments. X-ray diffraction （XRD）, photoluminescence （PL）, N2 adsorption Brunauer -Emmett- Teller （BET） method, UV-Visible diffuse reflectance spectroscopy （DRS）, transmission electron microscopy （TEM） were used to characterize the structure and composition of samples including crystal phase composition, crystalline sizes, optical property, typical specific surface area, light absorption, lattice structure and surface chemical state, respectively. Time-resolved surface photoconductivity （TRSP） and electron spin resonance （ESR） were used to probe the possible mechanism in the photocatalytic process.The phtocatalytic activity of novel composites was evaluated by degradation of Rhodamine B （RhB） in aqueous solution. The PZT/TiO₂ and PS/TiO₂ composites show much greater activity than that of separate PZT, PS, self-made TiO₂, the commercial photocatalyst P25, or many other visible irradiated photocatalysts in used.更多还原