Wen Bao-Ying, Lin Jia-Sheng, Zhang Yue-Jiao, Radjenovic Petar M, Zhang Xia-Guang, Tian Zhong-Qun, Li Jian-Feng
State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, College of Energy, Xiamen University, Xiamen 361005, China.
Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, Collaborative Innovation Center of Henan Province for Green Manufacturing of Fine Chemicals, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, China.
J Am Chem Soc. 2020 Jul 8;142(27):11698-11702. doi: 10.1021/jacs.0c05162. Epub 2020 Jun 23.
The electrical double layer (EDL) is the extremely important interfacial region involved in many electrochemical reactions, and it is the subject of significant study in electrochemistry and surface science. However, the direct measurement of interfacial electric fields in the EDL is challenging. In this work, both electrochemical resonant Raman spectroscopy and theoretical calculations were used to study electric field distributions in the EDL of an atomically flat single-crystal Au(111) electrode with self-assembled monolayer molecular films. This was achieved using a series of redox-active molecules containing the 4,4'-bipyridinium moiety as a Raman marker that were located at different precisely controlled distances away from the electrode surface. It was found that the electric field and the dipole moment of the probe molecule both directly affected its Raman signal intensity, which in turn could be used to map the electric field distribution at the interface. Also, by variation of the electrolyte anion concentration, the Raman intensity was found to decrease when the electric field strength increased. Moreover, the distance between adjacent Raman markers was ∼2.1 Å. Thus, angstrom-level spatial resolution in the mapping of electric field distributions at the electrode-electrolyte interface was realized. These results directly evidence the EDL structure, bridging the gap between the theoretical and experimental understandings of the interface.
双电层（EDL）是许多电化学反应中极为重要的界面区域，也是电化学和表面科学中重要的研究对象。然而，直接测量双电层中的界面电场具有挑战性。在这项工作中，电化学共振拉曼光谱和理论计算被用于研究具有自组装单层分子膜的原子级平整单晶Au(111)电极双电层中的电场分布。这是通过使用一系列含有4,4'-联吡啶部分作为拉曼标记的氧化还原活性分子来实现的，这些分子位于距电极表面不同的精确控制距离处。研究发现，探针分子的电场和偶极矩都直接影响其拉曼信号强度，进而可用于绘制界面处的电场分布。此外，通过改变电解质阴离子浓度，发现当电场强度增加时拉曼强度会降低。而且，相邻拉曼标记之间的距离约为2.1 Å。因此，实现了电极 - 电解质界面电场分布映射中的埃级空间分辨率。这些结果直接证明了双电层结构，弥合了界面理论和实验理解之间的差距。
