Into the “secret” double layer: Alkali cation mediates the hydrogen evolution reaction in basic medium

ABSTRACT The hydrogen evolution reaction (HER) – as an essential half reaction in water electrolysis and chlor-alkali process has been well studied in acidic electrolyte, but much less has been known in basic medium. In this study, by combining kinetic modeling and electrochemical measurements, we show that hydrated alkali cation clusters can adsorb on the surface of HER catalyst in basic electrolyte. The bound H2O molecules in the “clusters” can thus be in-situ activated through the hydration effect, which dissociate on the catalyst surface as the reactant of HER. The effective concentration and hydration energy of alkali cation can influence the H2O dissociation rate, and hence the kinetics of HER. Our work demonstrates a new understanding of the HER mechanism in basic reaction electrolyte.