基于二维层状极性半导体极化调控及其可见光光催化性能增强机制研究

The competition between recombination and transfer of photogenerated charge carriers is an important factor to determine photocatalytic efficiency. Till now, several strategies have been developed to enhance charge separation efficiency, which mainly focused on the interfacial charge transfer in photocatalytic composite system. This project focuses on the behavior of photogenerated charge carriers in semiconductor bulk. In terms of the intrinsic internal spontaneous polarization of polar semiconductor, we choose two-dimensional layered bismuth oxyhalides polar semiconductor to construct internal electric field to mediate photogenerated charge transfer and orientational transport in bulk, which could be similar to the role of the conventional interfacial electric field. Rationally tuning of internal polarization would be achieved by careful design of key unit of structure and component in layered bismuth oxyhalides. The general laws of internal polarization control and structure-activity relationship in polar semiconductor would be understand and revealed. Furthermore, it also clarifies the interrelation among internal polarization, self-built electric field and photogenerated charge separation. On the basis of these investigations, the generalized method for internal polarization tuning and the origin of optimized photocatalytic properties would be understand. It is expect to provide a new pathway to design and construct novel high efficient photocatalytic systems and to promote the development of the theory and application of photocatalysis.

光生电荷复合与转移之间的竞争是决定半导体光催化效率的重要因素。目前已经建立许多策略提高光生电荷分离效率，但主要集中于复合光催化体系界面电荷转移过程。本项目着眼于光生电荷体相行为，利用极性半导体本征的内部自发极化现象，选择二维层状卤氧化铋极性半导体构建与传统界面电场相似的内部极化电场介导光生电荷的体相转移与定向输运。通过对层状卤氧化铋关键结构功能单元设计实现其内部极化程度的调控。认识和揭示极性半导体内部极化调控的一般规律和构效关系。阐明内部极化、自建电场与光生电荷体相特性的内在联系。在此基础上，探讨极性半导体内部极化调控的通适性及其光催化性能择优的根源，期望藉此为新型高效光催化系统设计与构建开辟新途径，推动光催化理论和应用发展。

光生电荷行为主导着光催化反应过程，光生电荷复合与传输转移之间的竞争是半导体光催化效率的重要影响因素。本项目着眼于二维层状半导体材料中的光生电荷行为，发展多种策略介导光生电荷有效流动，促进光生电荷分离迁移，以增强其光催化反应活性。我们以具有可见光响应的层状极性半导体Bi3O4Br为研究对象，详细研究了内部极化电场协助下的光生电荷分离与传输机制，发现极性半导体Bi3O4Br在超声场所致的外加应力下会诱导产生内部极化电场，提出了极性半导体Bi3O4Br系统中压电-光催化协同过程。基于异质结构光催化剂中匹配能带的协同效应，构筑了多种具有良好光生电荷分离行为的光催化异质界面，如纳米片层异质结TiO2@C/g-C3N4、二维-二维层状异质结g-C3N4/MXene和Z-型Ag/AgCl/MOF等离子体型异质结，研究了这些体系中的光生电荷行为，发现能带匹配与维度协同可以促进光生电荷流动，从而提高层状异质结光催化材料的光催化性能。我们还将电催化活性材料（如MoS2，Co@NCNT，Co-Mo2C@NCNT）引入到二维层状光催化体系中，促进光生电荷的有效分离以及丰富反应活性位点，从原理上揭示了具有电催化活性助催化剂在光催化过程中的内在物理机制。