Impact of Water Coadsorption on the Electrode Potential of H-Pt(1 1 1)-Liquid Water Interfaces

Density functional theory molecular dynamics simulations of H-covered $\mathrm{Pt}(111)\text{\ensuremath{-}}{\mathrm{H}}_{2}\mathrm{O}$ interfaces reveal that, in contrast to common understanding, ${\mathrm{H}}_{2}\mathrm{O}$ coadsorption has a significant impact on the electrode potential of and plays a major role in determining the stability of H adsorbates under electrochemical conditions. Based on these insights, we explain the origin behind the experimentally observed upper limit of H coverage well below one monolayer and derive a chemically intuitive model for metal-water bonding that explains an unexpectedly large interaction between coadsorbed water and adsorbates.