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 hydrogen evolution reaction (HER) at gold (Au) electrodes. We show that at moderately alkaline pH (pH =11), increasing 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--OH δ- --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.