Reversible hydrogen spillover at the atomic interface for efficient alkaline hydrogen evolution

Ruthenium-based electrocatalysts exhibit promising potential as alternatives to platinum for catalyzing the hydrogen evolution reaction (HER) in alkaline media. However, the hydrogen binding ability and sluggish water dissociation kinetics of Ru catalysts require further optimization. Herein, we report a novel dual-site synergistic catalyst, Ru1-Mo2C, that simultaneously achieved high activity and stability for the HER via a reversible hydrogen spillover mode. The electronic metal-support interaction significantly modulated the charge redistribution of Ru1-Mo2C, resulting in an optimized d-band center and binding strength of H*. Density functional theory calculations revealed that water dissociation proceeded on Mo2C, and the generated hydrogen atoms were subsequently transferred to adjacent Ru single atom sites for H2 formation and release, enabling the reaction to adopt a reversible hydrogen spillover mechanism. As a consequence, Ru1-Mo2C exhibited an excellent HER performance with an ultralow overpotential of 10.8 mV at 10 mA cm-2 and mass activity of 8.67 A mgPGM-1 (@100 mV), which is 16.7 times greater than that of commercial Pt/C catalysts. Alkaline exchange membrane water electrolysis with Ru1-Mo2C as a cathodic catalyst achieved 1.0 A cm-2 at 1.83 V and remained stable at 500 mA cm-2 for over 200 hours. Ru1-Mo2C, a novel dual-site synergistic catalyst, demonstrated exceptional performance for the alkaline hydrogen evolution reaction (HER) through a reversible hydrogen spillover mechanism.