新型无支撑2D纳米片可见光光催化剂的制备及其界面电荷迁移机制研究

Designing and developing visible light-drived photocatalysts with high quantum efficiency is essential for photocatalysis. This proposal will study on novel, free-standing and visible light-drived 2D nanosheet photocatalysts with a molecular thickness and high photocatalytic performances. The interfacial charge transfer mechanism will also be investigated using their unique surface structures. Choosing appropriate precursors and solvents, a series of novel 2D nanosheet photocatalysts with large surface areas will be controllably prepared by soft-chemical methods based on both top-down and bottom-up strategies according to the Hansen solubility parameter theory. The effects of the solvents in reaction system on the sizes and thicknesses of 2D nanosheets will be systematically studied. The interaction relationships between the solvents with different surface energies, different intercalants and the substrates will also be unravelled. Furthermore, we try to study on the adsorption, activation, reaction processes of the reactants on the surface of photocatalysts in detail. After studying on electronic structures, optical excitations and interfacial charge mobilities, we can understand the key factors of raising the quantum efficiency of 2D nanosheet photocatalysts. Thus, the internal relationships between the component, structure, and properties of the photocatalysts will be clarified by combining with the calculation of quantum chemistry. And then, the possible visible light-drived photocatalytic mechanisms will be proposed and established. Finally, novel and visible light-drived 2D nanosheet photocatalysts with high quantum efficiencies are developed and a possible theory for the guidance of designing the photocatalyst with high activity will be revealed and proposed. It should be expected that the study on this proposal have the significant academic values in both theory and experiment for deeply understanding the intrinsic nature of photocatalysis from molecular level.

设计开发高量子效率可见光光催化剂是光催化领域的重点和难点。本项目拟开展研究分子级厚度的新型高效无支撑2D纳米片可见光光催化剂，并利用其独特的表面结构研究其光催化过程中界面电子迁移机制。根据Hansen溶解度参数理论，选择合适前驱体和溶剂，采用软化学方法自上而下或自下而上控制制备系列具有高比表面积的新型2D纳米片光催化剂。系统研究反应体系中溶剂对纳米片尺寸和厚度的影响，探明不同表面能的溶剂、不同类型插层剂与基体之间的相互作用规律。考察反应物分子在催化剂上的吸附、活化、反应等界面过程；研究纳米片的电子结构、光激发、光生载流子在界面中的迁移机制，确定影响活性的关键因素；结合量子化学计算，阐明催化剂的组成、结构与性能之间的关系，建立2D纳米片可见光光催化机理模型。最终，开发出高效新型2D纳米片可见光光催化剂，提出指导设计高效光催化剂可能的理论，为深入理解光催化的本质奠定理论和实验基础。

本项目基于自上而下策略开发了HNb3O8、HNbWO6、H3Ti5NbO14、C3N4等系列二维纳米片；利用自下而上策略制备出SnNb2O6、TiO2、SAPO-5分子筛等系列二维纳米片。这些二维纳米片材料在光解水、环境光催化、有机物选择性转化、CO2还原方面表现出了优异的性能和催化活性稳定性。同时为了提升其光催化活性，进一步利用贵金属和半导体修饰等方法来构建复合材料。研究了二维纳米片制备条件对于材料质量的影响，探讨了这一系列材料的组成、结构、表面态等对光催化性能的影响。利用分子光谱和原位表征手段，揭示了这些材料光催化反应过程本质，尤其是基于HNb3O8二维纳米片材料微观表面结构特性，从分子水平上阐明了苯甲醇在HNb3O8二维纳米片上的表面络合和光催化转化成苯甲醛的历程。这些研究成果将对超薄二维纳米片光催化剂的制备、结构调控以及分子水平上认识光催化作用提供重要的学术性指导作用，有效推动了光催化领域的发展。