Understanding hydrogen electrocatalysis by probing the hydrogen-bond network of water at the electrified Pt/solution interface

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 (Pt) in base by introducing N-methylimidazoles into the Pt-water interface. In situ spectroscopic characterization of the interface together with Quantum Mechanics computations showed that this promotion is caused by the N-methylimidazoles facilitating diffusion of hydroxides across the interface by holding the second layer water close to Pt surfaces. We accordingly propose that the HER/HOR kinetics of Pt in acid and base is governed by diffusion of protons and hydroxides, respectively, through the hydrogen-bond network of interfacial water by the Grotthuss mechanism, which accounts for the pH-dependent HER/HOR kinetics of platinum, a long-standing puzzle. Moreover, we demonstrated a 40% performance improvement of an anion exchange membrane electrolyzer by adding 1,2-dimethylimidazole into the alkaline solution fed into its platinum cathode.