光解水制氢纳米光催化材料的表界面基础研究

Photocatalytic water splitting is a promising route for producing hydrogen at semiconductor surfaces by utilizing water and solar energy. To design and fabricate highly efficient photocatalysts from a mechanistic perspective, it is of vital importance to realize the controllable synthesis of visible-light responsive model nanocatalysts with tunable surface and interface structures, which could be used to explore the microscopic mechanisms of the photochemical process at these locations. Based on density functional theory calculations, this proposal is aimed at designing photocatalysts with suitable band gap energies for visible-light absorption. With the selective exposure of high energy facets by controlling the reaction dynamics during the synthesis process, as well as the decoration of metal co-catalysts and the application of various thin film deposition techniques, highly controllable model catalysts with visible-light activity can be fabricated. By using state-of-the-art in-situ ultra-high vacuum surface science analysis techniques and in-situ dynamic spectroscopies, these model catalysts will be used to investigate the transportation of photogenerated charge carriers, the adsorption and activation of H2O molecules, as well as the evolution of intermediate species at the surface and interface of the semiconductor catalysts. From these observations, it is possible to develop new theories and methodologies for band gap engineering and surface/interface modification, which could provide new insights into the synthesis of photoelectrochemical water splitting electrodes or powdered nanoscale photocatalysts. Moreover, the selected promising photocatalytic systems will be further engineered to achieve a higher stability and superior gas evolving characteristics, which might be an important step forward in realizing large-scale solar water splitting for hydrogen production.

光催化水分解制氢利用太阳能在半导体表面将H2O分解为H2和O2，是一种理想的绿色制氢技术。具有可见光响应的纳米光催化材料的可控制备与表界面结构调控，以及表界面处的微观光化学机制的解析，是从机理层面设计高性能光解水制氢催化剂两个重要的基础性科学问题。本课题将基于理论计算设计并合成具有适宜能带结构的可见光光解水催化剂，并通过对合成动力学的控制实现其高能晶面的选择性暴露，此外通过金属助催化剂的负载和多种气相沉积技术制备模型光催化材料。在此基础上，借助先进的超高真空表面分析技术以及原位动态光谱表征技术，从分子水平上揭示纳米光催化材料表界面的电荷迁移、H2O分子吸附活化、中间产物演变等微观反应过程。基于此，发展和完善半导体催化剂能带和表界面结构调控的理论和方法，制备出高产氢效率的光电化学池光解水电极或悬浮态纳米光催化剂颗粒，并对具有一定前景的体系进行面向实际应用的稳定性和气体脱附性能的进一步优化。

光催化水分解制氢利用太阳能在半导体表面将H2O分解为H2和O2，是一种理想的绿色制氢技术。具有可见光响应的纳米光催化材料的可控制备与表界面结构调控，以及表界面处的微观光化学机制的解析，是从机理层面设计高性能光解水制氢催化剂两个重要的基础性科学问题。本项目基于密度泛函理论（DFT）计算，通过水热合成、电化学沉积、掠角沉积（GLAD）、原子层沉积（ALD）等方法制备了Fe2O3、WO3、BiVO4、CIGS、Si等光解水制氢电极，研究了其界面结构对光催化活性的影响。促进了半导体光解水催化材料对可见光的吸收，构建了光生电荷的高效传输通道，并提升了表面反应效率。筛选出p-Co3O4/n-BiVO4光电阳极，在1.23 VRHE偏压下的水氧化光电流达2.71 mA/cm2；以及CIGS/CdS/TiO2光电阴极，获得了高达9.3%的太阳能-氢能转化效率。此外，本项目还将研究拓展到了与光解水制氢高度相关的CO2光电还原，使含碳化合物的选择性达到92.6%。在本项目的资助下，在Nature Commun.、J. Am. Chem. Soc.、Angew. Chem. Int. Ed.、Adv. Mater.、Energy Environ. Sci.、Chem等重要国际SCI期刊上发表论文49篇，其中10篇入选ESI高被引论文，29篇被选为封面（扉页）论文，并应邀为Chem. Soc. Rev. 撰写综述。研究成果9次被Chemical & Engineering News（ACS）和 Materials Views（Wiley）等国际学术媒体报道。获2017年度天津市自然科学一等奖。