Wada, MelodyObata, KeisukeAgarwal, VenuLorenzutti, FrancescaHaussener, SophiaTakanabe, Kazuhiro2025-10-292025-10-292025-10-282025-10-2710.1021/acselectrochem.5c00299https://infoscience.epfl.ch/handle/20.500.14299/255333During the electrocatalytic hydrogen evolution reaction (HER), the second Wien effect enhances the dissociation of weak electrolytes when exposed to high electric fields. This enhanced dissociation impacts the reactant-switching mechanism, promoting the production of free protons that facilitate HER. In this study, we examine the extent of field-induced dissociation utilizing the generalized modified Poisson-Nernst-Plank (GMPNP) model, which incorporates electric-field-enhanced ion dissociation to simulate ion distributions and resulting proton limiting current densities in both unbuffered and buffered electrolytes. Specifically, we compare unbuffered conditions using KClO 4 with buffered systems using K-carbonate and K-phosphate. The findings reveal that strong field sensitivity may lead to an overestimation of water dissociation, especially in unbuffered conditions. Notably, in the presence of buffer species, field-enhanced protolysis allows free protons to serve as effective HER reactants at current densities exceeding several hundred mA cm −2. In the diffuse layer, the effective proton concentration surpasses that in the bulk due to the electric-field-driven dissociation of buffer species. This study emphasizes the critical role of interfacial electric fields in modulating local ion availability and highlights computational modeling as a powerful tool for visualizing nearelectrode ion distributions�an aspect challenging to capture experimentally.enSecond Wien effectelectric fieldion dissociationhydrogen evolution reactionelectrolyte engineeringtext::journal::journal article::research article