Reversed pH Dependence Behavior in Alkaline Environments for Hydrogen Evolution Reaction

The hydrogen evolution reaction (HER) typically shows a dependence on pH, with slower kinetics as the pH value increases, leading to sluggish kinetics under alkaline conditions. In our study, we unexpectedly observed an anomalous reversed pH dependence behavior in which the catalytic activity improves as the pH value increases on a Ru single-atom-doped WC electrocatalyst. In an alkaline solution, the catalytic performance of this catalyst surpassed that of Pt/C in acidic media. The mechanism of this pH reversed behavior was unlocked by considering both surface energetics and the interfacial microenvironment. Through density functional theory calculations, we revealed a significant improvement in the difference of the Gibbs free energy of H* adsorption with increasing pH, taking into account the applied potential and solution pH. At the interfacial environment level, the presence of Ru single atoms increased the water content in the gap, which enhanced the connectivity of hydrogen-bond networks and facilitated proton transportation. Our findings offer valuable insights into the underlying mechanisms responsible for the pH effect in the HER, thereby advancing the development of HER materials in alkaline environments.