State Key Laboratory of Physical Chemistry of Solid Surfaces, MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, iChEM, College of Chemistry and Chemical Engineering, College of Energy, College of Materials, College of Physical Science and Technology, Xiamen University, Xiamen, China.
School of Advanced Materials, Peking University, Shenzhen Graduate School, Shenzhen, China.
Nature. 2021 Dec;600(7887):81-85. doi: 10.1038/s41586-021-04068-z. Epub 2021 Dec 1.
Understanding the structure and dynamic process of water at the solid-liquid interface is an extremely important topic in surface science, energy science and catalysis. As model catalysts, atomically flat single-crystal electrodes exhibit well-defined surface and electric field properties, and therefore may be used to elucidate the relationship between structure and electrocatalytic activity at the atomic level. Hence, studying interfacial water behaviour on single-crystal surfaces provides a framework for understanding electrocatalysis. However, interfacial water is notoriously difficult to probe owing to interference from bulk water and the complexity of interfacial environments. Here, we use electrochemical, in situ Raman spectroscopic and computational techniques to investigate the interfacial water on atomically flat Pd single-crystal surfaces. Direct spectral evidence reveals that interfacial water consists of hydrogen-bonded and hydrated Na ion water. At hydrogen evolution reaction (HER) potentials, dynamic changes in the structure of interfacial water were observed from a random distribution to an ordered structure due to bias potential and Na ion cooperation. Structurally ordered interfacial water facilitated high-efficiency electron transfer across the interface, resulting in higher HER rates. The electrolytes and electrode surface effects on interfacial water were also probed and found to affect water structure. Therefore, through local cation tuning strategies, we anticipate that these results may be generalized to enable ordered interfacial water to improve electrocatalytic reaction rates.
理解固液界面上水的结构和动态过程是表面科学、能源科学和催化领域的一个极其重要的课题。原子级平整的单晶电极作为模型催化剂，具有明确的表面和电场特性，因此可用于阐明原子水平上结构与电催化活性之间的关系。因此，研究单晶表面上的界面水行为为理解电催化提供了一个框架。然而，由于体相水的干扰和界面环境的复杂性，界面水极难探测。在这里，我们使用电化学、原位拉曼光谱和计算技术来研究原子级平整的 Pd 单晶表面上的界面水。直接的光谱证据表明，界面水由氢键合和水合 Na 离子水组成。在析氢反应 (HER) 电位下，由于偏压和 Na 离子的协同作用，观察到界面水的结构从随机分布到有序结构的动态变化。结构有序的界面水促进了界面处的高效电子转移，从而提高了 HER 速率。还探测了电解质和电极表面对界面水的影响，发现它们会影响水的结构。因此，通过局部阳离子调谐策略，我们预计这些结果可以推广到有序界面水，以提高电催化反应速率。
