(Invited) The Cation Effects on the Alkaline HER/HOR Kinetics

Abstract

The sluggish kinetics of the hydrogen evolution and oxidation reactions (HER/HOR) in base remains unclear despite the fundamental importance of these reactions. Herein, we show that increasing the alkali metal cation (AM+) concentration promotes the HER while varying the identity of AM+ affects both HER/HOR. On the basis of these observations, we conclude that the presence of solvated AM+ anchored by OHad (OHad-(H2O)x-AM+) have two effects: (1) facilitating the OHad removal into the bulk forming OH--(H2O)x-AM+ as per the hard-soft acid-base (HSAB) theory, which selectively promotes the HER and makes the sharp HUPD peaks associated with the exchange of H/OH less reversible; (2) weakening the OHad binding energy to the surface, which hinders the HOR and the CO oxidation as per the bifunctional mechanism.