Effect of Water on Diffusion Energy Barriers of S ad on Cu(100) and Ag(100) Surfaces

High Resolution Image Download MS PowerPoint Slide We study the influence of liquid water on the surface diffusion of adsorbates on the electrode, which is an essential step in many electrochemical reactions. Density functional calculations show that water lowers the diffusion barriers of S ad on Cu(100) and Ag(100) surfaces compared to the situation in a vacuum. We use initial water layers generated by the Water Structure Creator by Dávila López et al. [ J. Chem. Phys., 2021, 155, 194702], relax them, and perform subsequent molecular dynamics simulations. These simulations lead to practically the same result as the relaxed configurations only. The water lowers the diffusion barriers of S ad on Cu(100) by 0.1 eV and of S ad on Ag(100) by 0.2 eV compared to the metal–vacuum interface. Complementary experimental studies of S ad diffusion on Cu(100) in 0.1 M HClO 4 were performed by high-speed electrochemical scanning tunneling microscopy. They find near the potential of zero charge hopping rates of 1 s –1 between neighboring sites, supporting the enhanced mobility in an aqueous environment.