Tian Ye, Huang Botao, Song Yizhi, Zhang Yirui, Guan Dong, Hong Jiani, Cao Duanyun, Wang Enge, Xu Limei, Shao-Horn Yang, Jiang Ying
International Center for Quantum Materials, School of Physics, Peking University, Beijing, P. R. China.
Electrochemical Energy Laboratory, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA.
Nat Commun. 2024 Sep 7;15(1):7834. doi: 10.1038/s41467-024-52131-w.
Water structures at electrolyte/electrode interfaces play a crucial role in determining the selectivity and kinetics of electrochemical reactions. Despite extensive experimental and theoretical efforts, atomic-level details of ion-specific water structures on metal surfaces remain unclear. Here we show, using scanning tunneling microscopy and noncontact atomic force microscopy, that we can visualize water layers containing alkali metal cations on a charged Au(111) surface with atomic resolution. Our results reveal that Li cations are elevated from the surface, facilitating the formation of an ice-like water layer between the Li cations and the surface. In contrast, K and Cs cations are in direct contact with the surface. We observe that the water network structure transitions from a hexagonal arrangement with Li to a distorted hydrogen-bonding configuration with Cs. These observations are consistent with surface-enhanced infrared absorption spectroscopy data and suggest that alkali metal cations significantly impact hydrogen evolution reaction kinetics and efficiency. Our findings provide insights into ion-specific water structures on metal surfaces and underscore the critical role of spectator ions in electrochemical processes.
电解质/电极界面处的水结构在决定电化学反应的选择性和动力学方面起着关键作用。尽管进行了广泛的实验和理论研究，但金属表面离子特异性水结构的原子级细节仍不清楚。在这里，我们使用扫描隧道显微镜和非接触原子力显微镜表明，我们能够以原子分辨率可视化带电Au(111)表面上包含碱金属阳离子的水层。我们的结果表明，Li阳离子从表面升高，促进了Li阳离子与表面之间形成类似冰的水层。相比之下，K和Cs阳离子与表面直接接触。我们观察到水网络结构从与Li的六边形排列转变为与Cs的扭曲氢键构型。这些观察结果与表面增强红外吸收光谱数据一致，并表明碱金属阳离子显著影响析氢反应动力学和效率。我们的发现为金属表面的离子特异性水结构提供了见解，并强调了旁观离子在电化学过程中的关键作用。
