We report direct observation of the formation of a subsurface species at metal electrodes in liquid electrolytes and of its migration within the solid's surface layer, below a chemisorbed electrochemical double layer. Using in situ video-rate scanning tunneling microscopy, we find for adsorbed sulfide on bromide-covered Ag(100) electrodes reversible transitions between adsorption sites on top of the surface and within a vacancy in the first Ag layer. In the latter state, the sulfide surface diffusion can be enhanced by orders of magnitude, which we attribute to vacancy-mediated diffusion underneath the bromide adlayer. The high dynamics within the surface layer, indicated by these observations, may open up alternative pathways in electrocatalytic reactions and growth processes.

中文翻译：

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电极处亚表面吸附物的形成和扩散

我们报告了直接观察到液体电解质中金属电极处的亚表面物质的形成及其在化学吸附电化学双层下方的固体表面层内的迁移。使用原位视频速率扫描隧道显微镜，我们发现溴化物覆盖的 Ag(100) 电极上吸附的硫化物在表面顶部的吸附位点和第一层 Ag 层的空位之间发生可逆转变。在后一种状态下，硫化物表面扩散可以增强几个数量级，我们将其归因于溴化物吸附层下方的空位介导的扩散。这些观察结果表明，表面层内的高动力学可能会开辟电催化反应和生长过程中的替代途径。