分子催化剂构建的复合光催化分解水体系研究

Solar water splitting is a promising approach to solve the global energy crisis. Overall water splitting is composed of water oxidation and proton reduction half reactions. Water oxidation has been considered as the bottle neck of overall water splitting due to the low quantum efficiency and poor longevity in both semiconductor-based photocatalytic water splitting system and homogeneous water splitting system. In this proposal, a new approach was suggested to overcome the above shortages and to establish a stable, efficient and low-cost artificial photosynthetic system by combination of light-absorbing semiconductor and molecular water oxidation catalyst. The contents of this proposal covers the design of the key components for oxygen evolution, construction of composite photocatalytic system, and the reaction mechanism study. As a result, water oxidation catalysts based on abundant metals such as Fe, Co and Ni will be prepared. Coupling with visible-light-absorbing semiconductor, their activity towards light-driven water oxidation will be investigated in a sacrificial system or in photoelectrochemical cell equipped with the semiconductor/molecular catalyst photoanode. This plan is expected to establish the fundamental principles for rational design of artificial photosynthetic system.

太阳光分解水制氢是解决当前能源和环境危机的一条理想途径，其核心环节是水氧化半反应和质子还原半反应。目前，半导体基光催化水氧化和基于分子催化剂的均相水氧化在量子效率、稳定性等关键指标上都难以令人满意，是制约整个体系发展的瓶颈。为建立高效、稳定、廉价的光解水体系，本申请提出可见光响应无机半导体和水氧化分子催化剂相耦合的光催化分解水新途径，以期充分发挥半导体作为捕光材料的稳定性和金属有机配合物高效催化产氧的优势。项目围绕水氧化体系关键组分的设计、光催化体系的构筑和反应动力学微观机制研究三方面内容，利用Fe、Co、Ni等廉价金属催化剂和n型半导体纳米材料相耦合构建复合产氧体系，确定半导体吸光材料和分子催化剂的匹配原则。制备半导体纳米材料/分子催化剂复合光阳极，组装高性能光电化学池（PEC），为实现人工光合作用体系的有效调控提供理论依据。

太阳能分解水制氢对于构建新能源体系具有重要意义，而水氧化反应是制约全分解水的科学瓶颈。为建立高效、稳定的光解水体系，本项目提出了可见光响应无机半导体和水氧化分子催化剂相耦合的光催化分解水新途径，以期充分发挥半导体作为捕光材料的稳定性和金属有机配合物高效催化产氧的优势。在过去的四年里，项目按照计划顺利实施，围绕半导体纳米材料/分子催化剂杂合光催化和光电催化体系的研究取得了一系列创新性成果，在J. Am. Chem. Soc.、Angew. Chem.、Adv. Energy Mater.等高档次学术期刊发表论文19篇，在相关领域培养博士研究生和硕士研究生8名，所取得的成果包括：（1）基于人工模拟酶分子催化剂发展了多个性能优异的杂合体系，构筑了新型太阳能转换复合材料。其中BiVO4/Co4O4立方烷光阳极在1.23 V vs. RHE 的光电流密度达到5 mA/cm2, 高于之前文献报道的所有未掺杂的BiVO4基光电极，光电转化效率（ABPE）接近2%。（2）以廉价金属无机盐和均相催化剂为前驱体，通过恒电位电沉积法制备了多种高活性、高稳定性金属氧化物析氧电极，其中CuOx作为产氧电催化剂为首次报道。开发了廉价FeOOH和具有高导电性、高比表面积的多孔碳相结合的高效介孔三维电极，催化性能在Fe基电极中处于领先。以上成果为发展具有应用前景的人工光合成体系提供了新契机。