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

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 approximate to 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-OH delta--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.

Automated summary

Increasing the alkali metal cation concentration enhances the activity of the hydrogen evolution reaction on gold electrodes, while increasing the electrolyte pH indirectly affects the reaction activity by tuning the near-surface cation concentration. However, too high near-surface cation concentration can lead to a decrease in the reaction activity due to surface blockage.