Lightweight porous Co3Mo/Co2Mo3O8 catalytic materials with enhanced hydrogen spillover for ampere-level water electrolysis

The Co 3 Mo alloy has attracted considerable attention due to its optimal hydrogen-binding energy for the alkaline hydrogen evolution reaction (HER). However, their HER kinetics under high current densities remain limited. Herein, a lightweight porous Ru-doped Co 3 Mo/Co 2 Mo 3 O 8 heterostructure supported on Ni foam is constructed to elucidate the mechanism by which hydrogen spillover enhances alkaline HER kinetics. In situ characterization and density functional theory (DFT) calculations reveal that the increased population of interfacial K⋅H 2 O species promotes water dissociation and enriches intermediate *H. Moreover, Ru doping effectively reduces the energy barrier between the metal and the support, thereby optimizing the adsorption energy of *H and accelerating hydrogen spillover kinetics from the metal to the support. The optimized catalyst exhibits outstanding HER performance in 1 M KOH, requiring an overpotential of only 180 mV at 1 A cm −2 . When integrated into an anion exchange membrane electrolyzer, the system delivers a cell voltage of 1.64 V at 1 A cm −2 (80 °C), demonstrating outstanding stability of over 500 h at 80 °C and over 1000 h at 40 °C. This study provides an effective strategy for catalyst design and identifies a promising class of candidate materials.