催化剂表面光生载流子分离以及光催化反应动态过程的原位液体池透射电镜研究

The efficient separation of photo-generated charge carriers is a key factor that impacts the activity of a photocatalyst, which makes studies on this issue significantly important. Liquid cell transmission electron microscopy (LC-TEM) can characterize the microstructures of a nano-scaled solid catalyst in solution. And in-situ studies on photocatalysis with LC-TEM technique is still at the very initial stage. There is no report on this issue about charge separation investigated by in-situ LC-TEM method by now..By combining our home-made photo TEM holder and liquid cell chips, this project aims to set up an in-situ LC-TEM system for photocatalysis studies. Utilizing this system, facet related photo-deposition process is to be deeply investigated, and the mechanism of this reaction is to be revealed. Then, photo-deposition process will act as a probing reaction for further studies on surface spatial separation of charge carriers. Furthermore, the surface reaction process and surface microstructure evolution of three model catalysts (i.e. particle with regular morphology, semiconductor loaded with co-catalyst, and heterojunction catalyst) will be studied by such method, to uncover the impacts of these three strategies on the spatial separation of charge carriers. Finally, surface active sites would be confirmed and mechanism of photocatalytic reaction process would be revealed. The results will provide a new example for in-situ characterization of photocatalytic reactions, and will offer evidences for designing photocatalysts with high performance.

光生载流子的有效分离是影响光催化活性的重要因素，具有重要的研究意义。液体池透射电镜技术可以实现溶液环境下纳米尺度固体催化剂的表面结构表征，利用该技术研究光催化过程的原位研究尚处于探索阶段，对光生载流子分离这一关键问题的研究尚未有报道。. 本项目旨在通过自制原位光样品杆以及液体池芯片相结合，搭建起一套可用于光催化反应原位研究的液体池透射电镜系统。在此基础上，首先对结构诱导光沉积现象进行原位研究，明确选择性沉积的本质，并以此作为研究光生载流子在催化剂表面分离过程的主体探针反应。更进一步，对具有规则形貌的样品、负载型催化剂样品以及异质结样品的表面光沉积过程以及表界面结构变化进行原位表征，验证这三种促进光生载流子分离的主流策略的作用，明确反应活性中心，揭示光催化过程的微观机理。以期形成一种新的光催化反应原位表征方法，为设计高活性的催化剂体系提供理论依据。

影响半导体光催化活性许多因素中，光生电子和空穴的有效分离是一个十分重要的因素，对这一过程的机理研究可以通过对光照过程中催化剂表面的结构变化的观察来实现。液体池透射电镜（LC-TEM）已经被证实是研究纳米粒子在溶液环境中结构变化的一种十分有效的手段。通过引入外部光源与液体池相结合，可以实现光催化过程的实时观测。.在本项目中，设计并成功试制了能够加载液体池芯片的原位TEM光样品杆，并对系统样品区域的照度和光强分布以及成像质量等进行了测试，达到实现光致反应的基本要求。利用光致Ag纳米三棱柱的生长反应对表征体系有效性进行了评价；进而，利用该系统对BPEI修饰TiO2纳米片载体表面的Au团簇的光致团聚机理进行了详细研究，证实Au团簇在载体表面的团聚遵循粒子迁移和奥氏熟化两种机制。利用该系统，对结构诱导光沉积现象进行原位研究，明确了电荷分离是选择性沉积的本质诱因，对理解光催化反应过程的微观机理具有重要的意义。