Proton shuttling at electrochemical interfaces under alkaline hydrogen evolution

Electrochemical water splitting is a promising method for sustainable hydrogen production, with alkaline electrolysis being a mature and cost-effective option for large-scale use. However, the hydrogen evolution reaction proceeds slowly in alkaline media, and its mechanism remains less understood than in acidic conditions. In particular, the role of alkali metal cations in water dissociation is unclear, despite their influence on hydrogen-bond structures of water. To investigate this, surface-sensitive terahertz spectroscopy is required for observing hydrogen-bond dynamics. Here, we show that interfacial water dynamics during hydrogen evolution reaction can be detected using surface-enhanced Raman scattering combined with vibrational analysis in a density-of-states format. Evidence from a KOH/Au interface shows that proton shuttling is facilitated by the constrained translational and rotational motion of water molecules around K⁺ ions. These findings provide molecular-level insights that could guide the design of more efficient alkaline electrolysis systems.