Decoupling Reaction Steps in Alkaline Hydrogen Evolution via a Ru/Mn3O4-x Cascade Electrocatalyst.

Abstract

Decoupling the kinetically mismatched elementary steps in the alkaline hydrogen evolution reaction (HER) is crucial for developing efficient electrocatalysts. Herein, we report a Ru/Mn3O4-x cascade electrocatalyst in which Ru nanoparticles are anchored onto an oxygen-vacancy-rich Mn3O4-x support. Theoretical calculations and spectroscopic characterizations reveal an electronic metal-support interaction mediated cascade mechanism, where the Mn3O4-x support serves as the primary site for water dissociation with a low energy barrier, while the generated hydrogen intermediates spontaneously spill over to adjacent Ru sites featuring a near-optimal hydrogen adsorption free energy, finally enabling efficient proton coupling and H2 evolution. This dual-site synergy delivers exceptional alkaline HER activity with an overpotential of only 21.4 mV at 10 mA cm-2, outperforming commercial Pt/C. When employed as a cathode in an anion exchange membrane water electrolyzer, the catalyst shows an ampere-level current density of 1 A cm-2 at a low cell voltage of 1.85 V. This work provides a decoupling mechanistic paradigm for designing high-performance alkaline HER electrocatalysts.