Mechanistic insights into pH-dependent hydrogen electrocatalysis by flipping interfacial water

Abstract

A grand challenge in electrochemistry is to understand and promote electrochemical processes by exploring and exploiting the interface. Herein, we promoted the hydrogen evolution and oxidation reactions (HER/HOR) of platinum in base by employing N-methylimidazoles to reorientate interfacial water against the interfacial electric field as evidenced by in situ spectroscopic characterization of the interface. We accordingly established a unified mechanism by which the HER/HOR in acid and base proceeds via diffusion of proton and hydroxide, respectively, through interface via interfacial water by the Grotthuss mechanism. This mechanism accounts for the pH-dependent HER/HOR kinetics of platinum, a long-standing puzzle. Furthermore, we demonstrated 40% performance improvement of an anion exchange membrane electrolyzer by adding 1,2-dimethylimidazole into the alkaline solution fed into its Pt cathode.