原位液体环境透射电镜研究TiO2光催化水裂解产氢机理

Understanding the reaction pathways of photocatalytic water splitting is of crucial importance for the development of renewable clean energy. As one of the most important photocatalysis, TiO2 has triggered broad interests and intensive studies, especially for studies on the mechanism of water splitting during photocatalysis. The chemical reaction of water with TiO2 under UV light, such as the adsorbed/desorbed state of water molecules on TiO2 surface, and the formation mechanism of hydroxyl groups, are both the interesting questions to be addressed. Up to now, however, the current microscopic methodologies to study these reactions mostly require the using of water vapor or are limited to molecule chemistry, which is far from the real phtocatalytic environment of TiO2 in liquid water. As the development of liquid environmental transmission electron microscopy (LETEM), it offers a great opportunity for in-situ exploration to study the dynamic reactions on TiO2 surface in water at nano even atomic-scale. The present proposal intends to develop an in-situ LETEM platform by a liquid holder, which is also equipped with the illumination of UV light. This can offer us a platform to dynamically explore the photocatalysis mechanism in water. This technical platform will be a feature of considerable scientific and technological interest, which allows the in-situ high-resolution observation of interfacial interactions between liquid water and TiO2. .There are two aims for this project. Firstly, we will design a experimental platform for the microscope, in which we will put the ilight llumination system into the TEM and observe the liquid environmental samples simultaneously. Another aim of this project is to study the evolution of microstructure on TiO2 surface based on this system, especially for the surface crystal structure, the chemical composition and valence state formed on the TiO2 surface in liquid water with the illumination of UV light. The TiO2 samples will be with rutile, anatase crystal structures and will be with different crytal plane explosured and metal nanoparticle supported. All of these studies may provide a new insight into the mechanism of photocatalytic water splitting on TiO2 that challenges the current understanding mechanism of photocatalytic surface chemical reactions. And this proposal enables a more effective exploration for highly efficient photocatalysts.

光催化水裂解产氢对清洁可再生能源的发展具有重要研究意义。TiO2作为典型光催化材料，其光催化水裂解机理研究，一直是当今科研领域的热点。然而，目前对TiO2/水界面结构的微观观察手段主要局限在水气氛中，其很难揭示出真实光催化条件下液态水中TiO2催化机理。尤其对于紫外光辐照前后，液态水中TiO2表面水的解离吸附状态变化、TiO2表面羟基化形成机制、以及羟基化表面对光催化效率的影响均未有深入的了解。最近发展的液体环境电镜技术，为原位观察研究液态水中TiO2表面微观结构变化提供了可能。.本项目将搭建原位电镜观察平台，能够实现在透射电镜中引入可控性光源，并观察液相样品；在此平台基础上，实现原位纳米、原子尺度观察光辐照过程中，液态浸润水环境中锐钛矿、金红石、不同晶面暴露以及负载型TiO2纳米颗粒的表面结构、化学成分以及价态演变规律，进一步揭示光催化剂表面化学结构变化对水裂解产氢过程的影响。

本项目旨在研发光照-液相环境透射电子显微镜样品杆系统，利用该系统，我们将研究光催化过程中，TiO2与水界面的晶体结构、液态水在TiO2表面的解离吸附状态、TiO2表面化学价态演变、以及液体中气泡的形成规律特征。.到目前为止，我们主要取得了三方面主要进展：1.研发成功了光照、电化学液相环境透射电子显微镜样品杆；2. 在此基础上，我们对液相环境中TiO2光催化反应过程进行了动态的观察与研究；3. 在此基础上，我们对电催化水裂解产氢过程中催化剂表面的演变特征进行了研究，尤其观察了催化剂反应过程中的相变过程。结果可以总结如下，利用光照液相环境透射电子显微镜，我们发现光催化产氢过程中TiO2催化剂表面会形成一层氢化层，该氢化层将有利于水裂解，并且有利于氢的脱吸附；除此之外，我们还观察了电催化OER过程中CoSx催化剂向CoOOH转变的过程，并且证明催化剂的反应位点为CoOOH，并且与初始合成的材料形貌以及化学组分无关。