期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 -, 期 -, 页码 -出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.2c02777
关键词
-
Understanding the collective behavior of ions at charged surfaces is crucial for geological and electrochemical processes. In this study, sum-frequency generation (SFG) spectroscopy was used to investigate the symmetry-breaking of water molecules at a charged silica surface in contact with different alkaline metal chloride solutions. The results demonstrate that the water response varies with the cation, with LiCl showing a significantly enhanced SFG response compared to CsCl. Further analysis indicates that the effect of different salts on the optical response is indirectly mediated by the reorganization of interfacial water.
Understanding the collective behavior of ions at charged surfaces is of paramount importance for geological and electrochemical processes. Ions screen the surface charge, and interfacial fields break the centro-symmetry near the surface, which can be probed using second-order nonlinear spectroscopies. The effect of electrolyte concentration on the nonlinear optical response has been semi-quantitatively explained by mean-field models based on the Poisson-Boltzmann equation. Yet, to explain previously reported ion-specific effects on the spectroscopic response, drastic ion-specific changes in the interfacial properties, including surface acidities and dielectric permittivities, or strong ion adsorption/desorption had to be invoked. Here, we use sum-frequency generation (SFG) spectroscopy to probe the symmetry-breaking of water molecules at a charged silica surface in contact with alkaline metal chloride solutions (LiCl, NaCl, KCl, and CsCl) at various concentrations. We find that the water response varies with the cation: the SFG response is markedly enhanced for LiCl compared to CsCl. We show that within mean-field models, neither specific ion-surface interactions nor a reduced dielectric constant of water near the interface can account for the variation of spectral intensities with cation nature. Molecular dynamics simulations confirm that the decay of the electrochemical potential only weakly depends on the salt type. Instead, the effect of different salts on the optical response is indirect, through the reorganization of the interfacial water: the salt-type-dependent alignment of water directly at the interface can explain the observations.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据