Kim Jaehyeon, Zhao Fujia, Zhou Shan, Panse Kaustubh S, Zhang Yingjie
Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA.
J Chem Phys. 2022 Mar 21;156(11):114701. doi: 10.1063/5.0080051.
The molecular structure of electric double layers (EDLs) at electrode-electrolyte interfaces is crucial for all types of electrochemical processes. Here, we probe the EDL structure of an ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPy-TFSI), using electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy. We extract the position and intensity of individual peaks corresponding to either intra- or inter-molecular vibrational modes and examine their dependence on the electrode potential. The observed trends suggest that the molecular reconfiguration mechanism is distinct between cations and anions. BMPy is found to always adsorb on the Au electrode surface via the pyrrolidinium ring while the alkyl chains strongly change their orientation at different potentials. In contrast, TFSI is observed to have pronounced position shifts but negligible orientation changes as we sweep the electrode potential. Despite their distinct reconfiguration mechanisms, BMPy and TFSI in the EDL are likely paired together through strong intermolecular interaction.
电极 - 电解质界面处双电层（EDLs）的分子结构对于所有类型的电化学过程都至关重要。在此，我们使用电化学壳层隔离纳米粒子增强拉曼光谱法探测离子液体1-丁基-1-甲基吡咯烷鎓双（三氟甲基磺酰）亚胺（BMPy-TFSI）的双电层结构。我们提取对应于分子内或分子间振动模式的各个峰的位置和强度，并研究它们对电极电位的依赖性。观察到的趋势表明阳离子和阴离子之间的分子重构机制不同。发现BMPy总是通过吡咯烷鎓环吸附在金电极表面，而烷基链在不同电位下强烈改变其取向。相比之下，当我们扫描电极电位时，观察到TFSI有明显的位置偏移，但取向变化可忽略不计。尽管它们的重构机制不同，但双电层中的BMPy和TFSI可能通过强分子间相互作用配对在一起。
