Phase-Engineered Ru-MoC Heterointerfaces for Efficient Alkaline Hydrogen Evolution by Boosting Interfacial Water Dissociation.

Abstract

Alkaline hydrogen evolution (HER) performance of Ru catalysts is limited by the high activation energy barriers of water dissociation and the poisoning of active sites by OH^* intermediates. Herein, the Mo_xC nanoclusters with distinct crystalline phases (MoC and Mo₂C) are supported on hierarchical N-doped carbon nanocages (hNCNC). Long-range disordered Ru nanoclusters are induced to grow on the MoC nanoclusters due to the presence of Mo vacancies, while crystalline Ru nanoclusters grow on both Mo₂C nanoclusters and hNCNC due to fewer defects. The Ru-MoC/hNCNC achieves an ultralow overpotential (@10 mA cm^-2) of 20 mV, a high turnover frequency of 21.8 H₂ s^-1 and robust durability in 1 M KOH, much superior to the counterpart of Ru-Mo₂C/hNCNC. The anion-exchange membrane water electrolysis device with Ru-MoC/hNCNC cathode delivers an industrial-scale current of 1 A cm^-2 at ≈1.65 V in 1.0 M KOH. The theoretical calculation, together with in situ Raman spectra, reveals that the Ru-MoC heterointerfaces promote the water dissociation kinetics on Mo sites, leading to the detached formation of OH^* on MoC and H^* on Ru. This spatial decoupling of OH^* and H^* can mitigate the OH^* poisoning of Ru and promote subsequent H₂ formation, thereby demonstrating excellent alkaline HER performance.