二氧化钛表面脱氢机理的理论研究

Photocatalytic technique is a new, energy-efficient and environmental friendly technique. TiO2 is attracting much attention because of its high photocatalytic activity, low toxicity and high stability. There are there key steps for producing H2 from TiO2 catalyzed water dissociation: the dissociation of water, the formation of H2, and the formation of O2. The water dissociation has been widely studied, and is well understood. In recently years, major experimental progress has been achieved in the field of H2 formation. It has been proved that H2 can be formed from the BBOH under thermal condition, and the efficiency can be increased by heavy metal adsorption or surface modification. The theoretical studies are therefore highly desired to understand the mechanism inside. In this project we will systematically study the hydrogen formation mechanism, as well as the influence of the BBO vacancy, the concentration of BBOH, the surface structure changes etc. With these results, we will investigate the competition of H2O and H2 formation from BBOH, and provide valuable suggestions for increasing the efficiency of H2 formation. Meanwhile, we will systematically investigate the mechanism of the H2 formation from heavy metal adsorbed TiO2 surface. We will also compare the reactivity of different adsorbed metal and different size of adsorbed cluster. Finally we should be able to provide theoretical support and valuable suggestions for design high efficient TiO2 system for H2 formation.

光催化技术是一种新兴的、高效节能的现代绿色环保技术，二氧化钛以其良好的光催化性能、化学性能稳定等优点被广泛使用和关注。二氧化钛光催化分解水制氢包括三个关键的化学过程，即水的解离，氢气的产生以及氧气的产生。其中水的解离研究最为广泛，也已经取得了一系列的重要研究成果。近年来二氧化钛表面的脱氢实验研究取得重大突破，已经证实表面桥氧氢可以在热化学条件下转化为氢气，并且转化的效率和条件可以通过表面的金属负载和改性进行改善。这些实验方面的突破急需理论研究的跟进与配合。本项目将系统研究二氧化钛表面的脱氢机制，以及表面氧空位、桥氧氢浓度、表面结构变化等因素对脱氢过程的影响。在此基础上分析脱氢和脱水的竞争关系，为提高脱氢效率提供理论指导。同时，我们将系统研究贵金属负载的二氧化钛表面的脱氢机制，分析不同金属，不同大小簇的负载对脱氢过程的影响，为设计具有更高脱氢效率的二氧化钛脱氢体系提供理论基础和建议。

二氧化钛光催化分解水制氢包括三个关键的化学过程，即水的解离，产氢以及产氧。本项目主要集中在二氧化钛表面的氢转移、脱氢及其相关化学过程的理论研究。我们发现了还原性TiO2(110)表面的脱氢机理是通过关键的Ti-H中间体进行，提出并通过理论研究证明增强表面的还原性对脱氢效率有着关键的作用。在此基础上考察了表面有机官能团负载和过渡金属负载两种提高还原性的途径对脱氢过程的影响。鉴于过渡金属负载能大大改善脱氢条件，我们系统研究了铂、金及其团簇在表面的吸附、迁移和团聚，及其对脱氢等过程的影响。另外，针对光催化过程，我们还对表面电子和空穴的分布及其对水解离过程的影响，对不同官能团的空穴捕捉能力进行了系统的理论研究。通过这些研究我们对二氧化钛表面的光解和产氢行为有了更加深入的认识，为开拓新型光催化体系提供理论基础。