表面态诱导的光生电荷微观行为与光催化体系的构效关系

In the photocatalytic system, surface state of the semiconductor materials often played the roles of free electron capture (or transfer) center or carrier recombination center. It has become one of the important factors affecting the photocatalytic reaction kinetics of photogenerated electrons and holes; Surface state is the "window" of photo-induced charges transfer, which influenced the behaviors of photo-induced charge generation, separation and migration so as to regulate the photocatalytic performance; Therefore, it’s important in the field of photocatalysis to thoroughly understand the surface state properties of photocatalytic materials, regulate and control the properties of surface states, and understand the regulation and control ability of surface states to the photo-induced charges. In this project, new photocatalytic materials with particular surface states properties will be designed and prepared. Combination of photocatalytic oxidation and reduction reaction, the position of surface states relative to the conduction or valence band positions will be investigated, and the binding energy of different surface states to photo-induced electrons or holes will be explored. More importantly, the relationship between behaviors of the photo-induced charge carriers and surface states will be revealed. The influence of surface states on the photocatalytic activities will be carefully illustrated. The investigation performed in this project on the regulation and control of surface states on the photo-induced charge behaviors is of fundamental and practical significance for the rational design and construction of novel materials with photocatalytic properties.

在光催化体系中，半导体表面态常常扮演着表面自由电子捕获（或转移）中心或载流子复合中心的角色，是影响由光生电子和空穴参与的光催化反应动力学的重要因素之一；表面态是光生电荷转移的“窗口”，通过对光生电荷的产生、分离、迁移与扩散等过程的影响，实现对光催化性能的调控。因此，深入了解光催化材料表面态性质，实现表面态性质的调控，了解表面态对光生电荷的调控能力是光催化领域的重要课题。本项目将制备系列具有特定表面态性质的光催化材料，结合光催化氧化和还原反应，研究表面态相对能带的位置，了解不同表面态对光生电子或光生空穴的束缚能，揭示表面态与光生电荷行为内在规律及对光催化活性的影响。该研究对于开发高效的光催化材料，从微观层面认识表面态对光生电荷行为的调控，促进光催化体系的实际应用具有重要意义。

在光催化反应中，表面缺陷对光催化性能影响的主要贡献来自于促进电荷分离和定向转移。准确解析表面态对光生电荷转移和传递的影响机制是构筑高效表面/界面缺陷型光催化体系的关键所在。本项目中，我们首先制备了一系列具有阴离子缺陷、金属/非金属掺杂的表面/界面缺陷型光催化剂，利用表面光伏技术、瞬态光伏技术、Kelvin探针技术和表面光伏场扫描技术对表面态的属性、能级位置、分布以及对光生载流子的束缚能力等性质进行解析；结合催化剂光降解有机污染物、水氧化、光电气敏和光解水产氢体系，研究了光生电荷在表面/界面缺陷型光催化体系中的分离、转移和传递的行为规律以及与活性之间的内在关系。研究表明，对于表面缺陷型光催化剂，构筑浅受体表面态有助于光还原过程的进行，引入给体表面态、钝化受体表面态有助于光氧化效率的提高；对于界面缺陷型复合材料，改变缺陷态性质，进行功函的调控，可以实现光生电荷在界面处的定向迁移，为光催化性能的提高提供动力。本项目所构建的表面态性质综合检测平台为深入理解构建缺陷半导体对光催化性能的提升提供了有力的参考。