不同晶面TiO2-C界面结构的构建及其在可见光催化过程中的行为研究

Due to their unique and controllable structural and electrical properties, the research and development of TiO2/C composite visible photocatalysts has been one of the most important fields in photocatalysis research. However, the relationship between the TiO2-C interfacial structure and its interaction mechanism remains to further research. Crystal facet control, on the other hand, has become an important strategy for fine-tuning the surface physicochemical properties of anatase TiO2. Although intensive experimental and theoretical studies have been conducted on the reactivity of different crystal faces of TiO2, much less attention is paid on the interaction between faceted TiO2 and carbonaceous materials. Based on this consideration, faceted TiO2/C hybrid materials are therefore designed in our project. Since the surface atomic arrangment and coordination changes with crystal faces in different orientation, a characteristic TiO2-C interface structure can be easily constructed by combining the carbonaceous materials and the TiO2 with oriented crystal faces. Investigateion into the TiO2-C interface characteristic stuctures will be the key to reveal the origin of the interaction (the mechanism of interfacial electron-transfer and their synergistic effect) between TiO2 and Carbon in the visible photocatalysis process. As to the analysis above, in this project, we proposed to synthesis various faces oriented TiO2/C hybrid materials to insight into the characteristic interface structure and the synergistic effect of TiO2-C. By optimizing the preparation technique, the microstructure of TiO2 (crystal face orientation and ratio of different facets) can be fine-tuned, and various faceted TiO2/C hybrid materials will be prepared successfully. Then, systematic researches will be taken to analyze the characterizations of TiO2-C interface structure (including surface atom arrangement and coordination, interface chemical bonding, and interface defective sites), the photon/electron responding feature, and the mechanism of interfacial electron-transfer. Based on the aforementioned work, we are going to set forth the synergistic effect of TiO2/C, and the dependence of visible photocatalytic properties on the TiO2-C interface characteristic structures. In general, the purpose of this project is to understand the relationship of compositions, microstructures, and visible photocatalysis performance of the TiO2/C hybrid nanocomposites. We believe that the systematic studies into the TiO2-C interface characteristic stuctures and interfacial electron-transfer are of great theoretical and practical significance. And, the outcomes of this project will give well support to the successful development of the high-performance TiO2/C photocatalysts.

揭示TiO2-C界面结构及其作用本质（两者耦合作用机理和界面电子转移行为）对于研发高效TiO2/C复合可见光催化剂具有重要意义。本项目基于对TiO2/C复合光催化材料的前期探索以及对不同晶面TiO2结构和催化行为的认识，提出构建不同晶面TiO2-C界面结构- - 研究TiO2-C耦合作用机理- - 揭示其可见光催化作用本质的新思路。 本研究拟通过锐钛矿TiO2纳米晶的微结构调控，实现具有特定界面结构的TiO2/C复合材料的可控制备；系统研究TiO2-C界面结构特征（不同晶面原子的排布和配位、界面化学成键和缺陷情况）、光电响应特性及界面电子迁移行为，阐明TiO2与碳间的耦合作用机理；从界面微结构及界面电子转移角度，分析TiO2/C复合材料的可见光光催化作用本质，揭示TiO2/C复合材料的组成－微结构－光催化性能之间的内在关系，为高效TiO2/C复合可见光催化材料的研发提供理论依据和实现途径。

二氧化钛/碳复合光催化材料的研发是光催化研究领域的一个重点课题，但目前TiO2-C间的协同协同耦合作用机理及其对可将光催化活性的具体影响仍存在争议。不论对于何种TiO2-C复合材料，良好的界面成键是其优异物化性能的前提，而界面成键通常又会引起纳米晶体缺陷的生成。缺陷是影响材料各项性能极其重要的因素，而在目前很多的TiO2-C复合材料的研究中却没有得到足够的重视。. 在本项目的支持下，我们采用一步法合成系列TiO2@C复合材料，通过系统表征发现含碳前驱体的缩聚为TiO2的结晶提供条件，并与TiO2表面形成Ti-O-C键，同时产生氧缺陷（VO）。结果表明VO浓度与TiO2的吸收带边红移之间存在一致对应关系（产生杂质能级），增强了界面电荷的转移能力，降低了光生电子-空穴对的复合效率，是TiO2具备优良可见光响应性能的决定性因素。此外，适量的碳还能提高界面氧缺陷的寿命，并提高复合材料对污染物的吸附能力。基于上述结论，我们利用光化学反应法制备了带有界面氧缺陷的2-萘酚/TiO2复合可见光催化材料，结果进一步证实了界面缺陷能够优化TiO2的光吸收性质，并提高界面电荷传输效率以及增加载流子的寿命，而2-萘酚构成的无序层状聚合物可有效保护缺陷，提高其寿命和环境光催化性能。. 另一方面，无机纳米材料的催化活性与其所暴露晶面的物理化学性质密切相关。通过合成一系列不同晶面取向的TiO2并与C复合形成TiO2@C复合材料，我们发现TiO2表面F的存在有助于C材料在TiO2表面的键合，并在一定程度上提升其可见光活性，然而界面缺陷仍然是该复合材料具备可见光响应的关键。利用苯甲醇有氧光催化反应在TiO2表面引入氧缺陷，可进一步合成出具有可见光活性的TiO2-VO@C复合纳米材料。同时TiO2的晶面取向仍然是影响其活性高低的重要因素。本研究结果有助于深入认识TiO2/C纳米复合材料制备和性能的影响要素，为新型高效TiO2/C复合材料的设计和制备提供指导。