片状Bi4Ti3O12/TiO2异质结构材料的合成及其可见光催化机理

Textured micron scale Bi4Ti3O12 platelets with layer-perovskite structure and controlled mophology and size are synthesized by molten salt method. Using the Bi4Ti3O12 precursor, Nano-sized TiO2 particles grow along the surface of Bi4Ti3O12 templates through hydrothermal treatment or hydrolysis of titanium sulfate, and then form <001> textured heterostructured Bi4Ti3O12/TiO2 composite. We begin with a survey of efforts to explore the energy band configuration of the Bi4Ti3O12/TiO2 composite, clarify the photocatalytic mechanism and analyze the influence factors to improve the photocatalytic activities. Based on the theoritical research above, we design the resonable interface to get the high property micro/nano sized material systerm through facile method. The photocatalytic activity of Bi4Ti3O12/TiO2 are measured with the photodegradation over methylene blue at room temperature under visible light irradation,the composite show good absorption in the visible region and the photodegradation against methylene blue should be better than the commercial TiO2(P25);Study the mechanism of the photocatalytic activity, build a model about the electricity transfermation between the ferroelectrics and the photocatalytic materials; The heterostructured Bi4Ti3O12/TiO2 composite combine the advantages of each of the end composition,it could be used to save the energy efficiency in buildings and the treatment of the waste water.

本项目采用熔盐法合成具有可控形貌、尺寸和织构的层状钙钛矿型微米级片状Bi4Ti3O12晶体，并以此为模板前驱体，通过水热或硫酸钛水解法使纳米TiO2 粒子沿模板前驱体表面均匀结晶生长，得到<001>方向织构化并具有异质结构的Bi4Ti3O12/TiO2复合材料；研究片状Bi4Ti3O12/TiO2界面处的物质结构及能级结构，探索铁电材料的光电转换机制，阐明复合材料异质结构的可见光催化机理，分析提高其光催化性能的主要因素。在上述理论研究的基础上，设计合理的界面结构，通过简单的制备工艺获得性能优异的微米/纳米异质结构材料体系，以亚甲基蓝为模拟污染物，短时间内的光降解效率优于商业化的P25 TiO2；完善铁电材料的光催化理论，建立铁电-光电动态转换模型；Bi4Ti3O12/TiO2异质结构材料结合了铁电材料与光电材料的优势，在建筑节能、污水处理等领域有较大意义和应用价值。

使用半导体光催化材料降解污染物是目前应用于环境净化方面的新方向。本项目系统研究了层状-钙钛矿结构Bi4Ti3O12材料的制备，Bi4Ti3O12/TiO2复合材料的界面设计及光催化性能。主要得到了以下结果：.1.不同的熔盐热处理工艺能够得到具有不同方向比（长宽/厚度）的微米级Bi4Ti3O12晶体，钙钛矿结构及片状外形有利于材料的光催化性能的提高，晶体内部层状结构为材料的比表面积以及光生电子对的输运起到了积极作用。.2.确定了Bi4Ti3O12/TiO2复合材料的界面设计原则，得到了较基体材料更加优异的光催化性能。采用浸渍提拉复合法、水解硫酸钛复合法和溶胶包覆法分别得到了Bi4Ti3O12/TiO2薄膜和片状粉体复合材料；.研究了各向同性的Bi4Ti3O12/TiO2复合材料的制备工艺，以工艺简单可控的TiO2球为模板，二步反应法得到了亚微米级的球形复合材料；复合材料均能在短时间内降解亚甲基蓝等模拟污染物。.3.研究了Bi4Ti3O12/TiO2界面处的物质结构及能级结构，指出铁电材料自发极化的内电场与能带结构的构筑是促进光生电子快速分离并输运的主要因素，而微米纳米尺度的界面结合能更加有效的促进光催化的性能。.本项目建立了材料结构和性能的实验联系，发展了相应的制备技术，并进一步探索了Bi4Ti3O12/SrTiO3等新的二元体系复合材料，以期得到良好的光催化效果，为我国发展高性能光催化材料提供基础。