K. Obata, L. Stegenburga, K. Takanabe
Journal of Physical Chemistry C, (2019)
Although electrochemical hydrogen evolution reaction (HER) on a Pt electrode is among the most studied electrocatalytic reactions, its reaction mechanism and exchange current density are still under debate. Particularly on the Pt catalyst, its facile reaction kinetics and lack of effective methods to compensate mass transport makes it difficult to isolate kinetic and diffusion contributions. This study focuses on the quantitative description of mass transfer contributions in buffered near-neutral pH regions, which are relevant to various (photo-) electrochemical reactions for water splitting and CO2 reduction. The established model quantitatively breaks down the observed overpotentials with diffusion contributions of both hydrogen and buffer species while the intrinsic kinetics on Pt exhibits negligible contribution. The significance of electrolyte engineering, i.e., the optimization of the electrolyte identity and molality, is confirmed to determine the overall performance of hydrogen evolution reaction.