二氧化钛光解水制氢表面反应动力学过程的理论研究

Photocatalytic water-splitting is a dream reaction for the conversion of solar enenrgy to chemical enenrgy and semiconductor metal oxides are always used as the photocatalyst. The whole process of photocatalysis is quite complicated including the light absorption,the generation and evolution of electrons and holes and at last their interation with surface adsorbed molecules. Thus, the investigation of the kinetic processes of surface reactions are meaningful for understanding the whole processes of photocatalysis. In this proposal, focusing on photocatalytic water-splitting processes by titanium dioxde based materials, we try to construct a methodology for the investigation of photo-induced surface processes based on density functional theory plus U (DFT+U) method combined with spectra simulation,molecular dynamics simulation, theomodyanmics anyalisis. Firstly, we will inveistigate the trapping states of electron and hole on TiO2 materials with various facets, defects or adsorbates, different shape and size. Secondly, the whole process of the geneartion of O2 and H2 by the interaction of trapped electrons and holes with water molecules in vacuum will be studied. And at last based on previous results, we will investigate the whole kinetic processes of water-splitting in solvant with different tinatium oxide surfaces or nanoparticles and try to find the rate-limitting step of the generation of O2. We hope our investigations could provide some useful hints for the experimental synthesis of photocatalyst with high catalytic activities.

光催化分解水制氢是太阳能-化学能转换研究的重要方向之一。半导体金属氧化物是常用的光催化剂，光催化过程非常复杂，反应最后通过光生电子、空穴在表面上和反应物分子相互作用而实现，因此理解表面电子、空穴的俘获状态及其与分子反应的完整表面动力学过程对理解光催化机制有着重要意义。本项目基于DFT+U方法，结合谱学模拟、分子动力学模拟、热力学分析等方法，构建表面光化学过程在同一理论框架下的普适研究方案，围绕二氧化钛光解水制氢反应，系统开展如下工作：1）晶面、缺陷、尺寸形貌、分子与表面的相互作用等对电子、空穴表面俘获状态和位置的影响；2）俘获电子、空穴与表面低覆盖度分子相互作用直至生成氧气和氢气的完整动力学过程；3）水溶液中生成氢气和氧气的动力学过程，揭示整个反应的速控步，为光催化剂的设计、改进提供理论依据和指导。

项目按计划执行。主要研究内容是构建基于DFT+U研究二氧化钛光解水机制的方案，探索提高光解水活性的方法。主要研究进展包括：(1)提出金属原子掺杂及表面羟基化共同作用对二氧化钛薄层材料光吸收性能及电子-空穴分离性能的提高；(2)揭示金属原子掺杂对水解离性能的提高；(3)揭示不同金属掺杂及掺杂浓度对析氢性能的影响；(4)揭示应力对析氢性能的影响；(5)揭示氧化铁在非贵金属掺杂时OER性能的提高机制；(6)揭示Co3O4纳米薄片体系对二氧化碳电还原活性的提高机制；(7)揭示Rh掺杂氧化亚钴纳米薄片对碳链增长反应产物高选择性的机制；(8)揭示二维材料高浓度掺杂时对化学反应通道的调控机制。这些研究成果已在Nature Nanotechnol.，Nature Commun.，ACS Catal. 等杂志发表标注文章9篇，另有4篇在投中和整理中的结果。在国内外学术会议上做邀请报告2次。协助培养博士生1名，2名硕士生转博。