Atomically thin photoanode of InSe/graphene heterostructure

很多物理和化学过程都发生在固体电极与溶液的表界面处，因而表面处离子的吸附、聚集及其在表面的反应都对整个反应过程起到至关重要的作用。然而使用传统的固体电极通常表现出的是体相和表面的复合性质，使得单纯研究电极材料表面效应及表面离子的动力学还存在挑战。二维材料由于其具有单原子层的厚度，晶体中所有原子都处在表面，因而可以作为一种理想的模型体系来仅针对此类表面现象进行研究。课题组选择光电化学池（PEC）分解水反应中的决速步骤氧析出半反应（OER）以作为研究表面离子行为的探针反应。光电极选择同时具有高迁移率、匹配的能级结构以及被抑制的光生电子-空穴复合的单层的二维硒化铟（InSe）材料。并且在手套箱提供的惰性气氛中用单层石墨烯对InSe进行封装，保证了光电极测试条件下长时间的稳定性。该工作揭示了二维异质结表面性质与反应活性的内在联系，希望能为研究电极表面离子效应提供新的材料平台。后续通过选择具有合适表面性能的二维材料，并与传统光电极材料结合，有望发展新型的高性能光阳极材料。 这一研究工作的实验部分是在化学化工学院曹阳教授指导下完成，博士生郑海红、鲁艺珍与广东工业大学轻工化工学院叶凯航博士为论文的共同第一作者。理论计算部分在程俊教授的指导下，由博士生胡晋媛完成。Achieving high-efficiency photoelectrochemical water splitting requires a better understanding of ion kinetics, e.g., diffusion, adsorption and reactions, near the photoelectrode's surface. However, with macroscopic three-dimensional electrodes, it is often difficult to disentangle the contributions of surface effects to the total photocurrent from that of various factors in the bulk. Here, we report a photoanode made from a InSe crystal monolayer that is encapsulated with monolayer graphene to ensure high stability. We choose InSe among other photoresponsive two-dimensional (2D) materials because of its unique properties of high mobility and strongly suppressing electron–hole pair recombination. Using the atomically thin electrodes, we obtained a photocurrent with a density >10 mA cm−2 at 1.23 V versus reversible hydrogen electrode, which is several orders of magnitude greater than other 2D photoelectrodes. In addition to the outstanding characteristics of InSe, we attribute the enhanced photocurrent to the strong coupling between the hydroxide ions and photogenerated holes near the anode surface. As a result, a persistent current even after illumination ceased was also observed due to the presence of ions trapped holes with suppressed electron-hole recombination. Our results provide atomically thin materials as a platform for investigating ion kinetics at the electrode surface and shed light on developing nextgeneration photoelectrodes with high efficiency.The experimental work was supported by the National Key R&D Program of China (2018YFA0306900 and 2018YFA0209500), the National Natural Science Foundation of China (21872114), and China Postdoctoral Science Foundation (2020M682616). 该工作得到了国家重点研究计划（2018YFA0306900、2018YFA0209500），国家自然科学基金（21872114）、中国博士后科学基金（2020M682616）的支持