铁酸铋Z型异质结的构建及可见光催化分解水应用研究

Hydrogen generated by photocatalytic water splitting under the sunlight is of critical importance for the development of the clean and sustainable energy. As one of important factors in the system, light absorption materials play an important role for the performance improvement. BiFeO3, as a narrow direct band gap semiconductor, has the ability of oxygen generation from water splitting in visible light. Nevertheless, the application in photo-to-electric conversions has been restricted due to the fast recombination between photo-induced electron and hole and the poor injection efficiency of hole. There is an effort to product hydrogen by photoelectrochemical water splitting based on doped BiFeO3 Z-heterojunction photoanode: (1) Doped BiFeO3 will be prepared with a lot of advantages, such as wide range response in visible light and flexible doping energy level around conduction band. (2) Z-heterojunction photoanode BiFeO3/RGO/CdS will be assembled from hydrothermal process. Photo-induced electron and hole can migrate and recombination quickly through RGO to avoid self-recombination. (3) Merged into the co-catalyst, hole injection efficiency and integrated efficiency of the heterojunction can be improved at the same time. We do our best to realize the high-efficient photoelectrochemical water splitting based on BiFeO3/RGO/CdS Z-heterojunction photoanode and expose the mechanism. Not only efficiency, but also stability of photoelectrochemical water splitting could be promoted based on the multiferroic photoanode.

利用太阳能在光催化体系下分解水制氢是新能源研究的一个热点问题。作为该体系研究核心之一的吸光材料对其性能的提升起重要作用。铁酸铋(BiFeO3)作为较窄带隙半导体，具有可见光催化分解水制氧的能力，然而其较高的光生电子空穴复合率及较低的空穴注入效率限制了其光电转换应用。本项目拟开展掺杂BiFeO3的Z型异质结光阳极进行光电化学分解水研究。第一，制备具有可见光响应范围宽、导带附近掺杂能级可调的掺杂BiFeO3纳米结构；第二，采用水热法构建BiFeO3/RGO/CdS的Z型异质结光阳极，通过光生电荷在RGO上的快速迁移、复合来抑制光生电子空穴的体相复合，提升电荷分离能力；第三，引入助催化剂，增加空穴注入效率，提高异质结电极分解水的综合性能。最终通过BiFeO3 Z型异质结光阳极光电化学分解水体系的构建及载流子高效传输机制的研究，全面提升以多铁材料为基础的光阳极在光电化学电池应用上的综合性能。

利用无机半导体光催化剂在可见光下实现高效稳定分解水是应对能源危机和环境污染的理想解决方案之一，光催化分解水技术的开发应用和产业化的加速推进对我国双碳目标的实现具有直接的推动作用。本课题围绕铁酸铋Z型光催化剂的设计、组装、改性、机理探究等方面开展研究工作，通过对空间构效关系、界面耦合效应、表面电荷差异性分布特性三者的协同关系探索，完成了Z型光催化剂体系从理论设计到实验制备再到性能提升最后到机制揭示的全链条研究，揭示了光生载流子在不同异质结界面间传输速度的决定因素及在单原子修饰的二维助催化剂表面迁移寿命的影响机制。具体结论如下：具有晶格强匹配作用的异质结界面可以提供载流子的快速迁移通道；二维析氢、析氧助催化剂的表面改性对电荷的差异性分布及载流子寿命都有着很大的影响；助催化剂表面单原子缺陷的引入策略提升其催化剂活性的实质原因是加速载流子的定向传输和促进电荷的差异性分布。对二维助催化剂的表面单原子缺陷修饰研究发现该策略可彻底激活二维表面原子的催化活性，实验和理论研究均表明通过单原子空位缺陷策略打破二维助催化剂表面电荷均态分布特性可有效提升载流子的迁移速率及寿命，大大提升分解水的催化活性。性能测试结果表明可见光下光催化体系可获得70 mmol h-1 g-1的极限产氢速率，超越了绝大部分已报到的光催化剂的产氢速率，并且可以实现连续40小时的稳定产氢寿命。在析氢、析氧助催化剂催化活性方面，实现了50 mV vs10 mA cm-2的高活性产氢数据和1.42 V vs 10 mA cm-2的高活性产氧数据，且可连续稳定工作100小时，综合性能远超商品级贵金属电极。该项目的顺利实施对于设计、制备高性能可见光催化分解水催化剂具有较好的支撑和启发的作用。