半导体材料/分子催化剂复合构建高效、稳定的光电化学分解水产氢、产氧器件

The production of hydrogen by sunlight-driven water splitting is one of the promising solutions to the problems of global energy shortage and CO2 over-emission. Studies on the earth-abundant element-based photoelectrochemical cells that can efficiently split water into H2 and O2 under irradiation of sunlight are of obviously scientific significance and potential application for realization of large-scale H2 production by photoelectrolysis of water. In this project, a pioneering effort towards this end will be made. The highly efficient non-noble metal-based HER (hydrogen evolution reaction) and OER (oxygen evolution reaction) molecular catalysts will be respectively anchored onto the electrode surface of inexpensive semiconductive materials via covalent multipoint bonding or coordinate self-assembling, to build highly efficient and durable photoelectrode devices using semiconductor/molecular catalyst composites for H2-production and O2-evolution. The photoinduced charge separation and carrier mobility at photoelectrodes as well as the mechanisms for photocatalytic H2- and O2-generation will be deeply explored, and the influence of various molecular catalysts and anchoring units on the charge transfer, photocurrent, photovoltage, and catalytic activity of semiconducting material electrodes will be revealed. The prepared O2-releasing photoanodes and H2-producing photocathodes will be evaluated and optimized respectively to improve the activity and stability of the photoelectrodes. The final step of this project is to couple the most active photoanode and photocathode to construct a cost-effective and environmental benign photoelectrochemical cell that can spontaneously split water into H2 and O2 in high efficiency under sunlight irradiation.

利用太阳能光解水制氢是解决全球能源短缺和二氧化碳过度排放问题的理想方法之一。研制基于地球富含元素的、能够在太阳光驱动下高效分解水的光电化学反应器件，对于实现大规模光解水制氢具有重要的科学意义和潜在的应用价值。本项目旨在通过多位点共价键合方式或配位自组装等方法，将高效的非贵金属质子还原产氢和水氧化放氧反应分子催化剂，分别锚定在与之能级匹配的廉价的半导体材料电极表面，构建分子催化剂与半导体材料复合型高效、稳定的产氢和产氧光电极器件；深入研究光电极上光生电荷分离和载流子迁移动力学和催化产氢、产氧反应机理，揭示各种分子催化剂以及桥连单元对半导体材料电极光生电荷转移、光电流、光电压以及催化反应活性的影响规律；在分别评价和优化放氧光阳极和产氢光阴极器件的基础上，组装具有应用前景的材料经济、环境友好的光电化学水裂解反应器，实现仅用太阳能驱动无需外加偏压的连续高效光解水同步产氢、产氧。

光电催化水裂解是最有希望的大规模制氢技术之一。研制高效、稳定、廉价的产氢、产氧光电极并构建以太阳光为唯一能源的全分解水光电化学池，是实现光驱动高效、低成本分解水制氢的重要应用基础研究工作。将具有高催化产氢活性的N4-和N5-配位的钴、镍分子催化剂锚定在p-Si和Cu2O半导体光阴极上，制备了十多种分子催化剂/半导体杂合光阴极，系统研究了催化剂分子结构、锚定基团以及连接链对电极界面电子转移和电荷复合动力学以及光电催化产氢性能的影响。通过优化分子催化剂和锚定基团成功构建了p-Si/TiO2/Ni(N5)杂合光阴极，其光电催化产氢活性和稳定性都优于文献报道的分子催化剂化学键合修饰的不含镓的半导体光阴极。构建了三种硅基/无机催化剂复合光阴极，证明了在p-Si与TiO2之间插入氮掺杂的石墨烯纳米层和在p-Si表面形成TiO2纳米柱阵列，是行之有效且操作简便的提高硅电极的光致产氢活性和稳定性的方法。设计合成了多齿氮螯合配位的铜、镍高效水氧化分子催化剂，揭示了配合物骨架的刚性、配体的共轭性质以及二级配位环境对分子催化剂催化活性和稳定性的影响规律。研发了高效、稳定的Fe/V或B掺杂的镍基水氧化催化剂，从原子层面剖析了在催化产氧过程中多元金属催化剂中不同金属原子之间的相互作用和微观配位环境的变化。通过长碳链烷基的疏水作用将Co4O4簇合物负载到BiVO4光阳极表面，制备了水氧化杂合光阳极。将p-Si/TiO2/Ni(N5)光阴极与BiVO4/Co4O4-R光阳极耦合，成功构建了无贵金属、无光敏剂的生物模拟光电化学池，实现了在模拟太阳光照射下、无偏压全分解水连续产氢、产氧，光-氢转化效率为0.04%，高于迄今为止报道的分子催化剂修饰的光电化学池的效率。这是第一例基于分子催化剂修饰的半导体光阳极和光阴极、能够实现在光照下无偏压完全分解水的生物模拟Z-scheme光电化学反应池。