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High Resolution Image Download MS PowerPoint Slide During 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 near-electrode ion distributions─an aspect challenging to capture experimentally.
Wada et al. (Mon,) studied this question.