The Interrelated Effect of Cations and Electrolyte pH on the Hydrogen Evolution Reaction on Gold Electrodes in Alkaline Media

• Published in: Angewandte Chemie International Edition 2021-06, Vol.60 (24), p.13452-13462
• Main Authors: Goyal, Akansha, Koper, Marc T. M.
• Format: Article
• Language: English
• Subjects: Alkali metals; Cations; electrocatalysis; Electrodes; Electrolytes; Field strength; Gold; hydrogen evolution reaction; Hydrogen evolution reactions; Metal concentrations; Metal ions; pH effects; Water chemistry
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202102803

In this work we study the role of alkali metal cation concentration and electrolyte pH in altering the kinetics of the hydrogen evolution reaction (HER) at gold (Au) electrodes. We show that at moderately alkaline pH (pH 11), increasing the cation concentration significantly enhances the HER activity on Au electrodes (with a reaction order ≈0.5). Based on these results we suggest that cations play a central role in stabilizing the transition state of the rate‐determining Volmer step by favorably interacting with the dissociating water molecule (*H–OHδ−–cat+). Moreover, we show that increasing electrolyte pH (pH 10 to pH 13) tunes the local field strength, which in turn indirectly enhances the activity of HER by tuning the near‐surface cation concentration. Interestingly, a too high near‐surface cation concentration (at high pH and high cation concentration) leads to a lowering of the HER activity, which we ascribe to a blockage of the surface by near‐surface cations. The kinetics of the hydrogen evolution reaction (HER) at gold electrodes is affected by the concentration of alkali metal cations and electrolyte pH. At moderately alkaline pH, increasing the cation concentration greatly enhances the HER activity. Cations are proposed to help stabilize the transition state of the rate‐determining Volmer step by a favorable interaction with the dissociating water molecule (*H–OHδ−–cat+).