Bimetal Modulation Stabilizing a Metallic Heterostructure for Efficient Overall Water Splitting at Large Current Density

Abstract Large current‐driven alkaline water splitting for large‐scale hydrogen production generally suffers from the sluggish charge transfer kinetics. Commercial noble‐metal catalysts are unstable in large‐current operation, while most non‐noble metal catalysts can only achieve high activity at low current densities 500 mA cm−2). Herein, a sulfide‐based metallic heterostructure is designed to meet the industrial demand by regulating the electronic structure of phase transition coupling with interfacial defects from Mo and Ni incorporation. The modulation of metallic Mo2S3 and in situ epitaxial growth of bifunctional Ni‐based catalyst to construct metallic heterostructure can facilitate the charge transfer for fast Volmer H and Heyrovsky H2 generation. The Mo2S3@NiMo3S4 electrolyzer requires an ultralow voltage of 1.672 V at a large current density of 1000 mA cm−2, with ≈100% retention over 100 h, outperforming the commercial RuO2||Pt/C, owing to the synergistic effect of the phase and interface electronic modulation. This work sheds light on the design of metallic heterostructure with an optimized interfacial electronic structure and abundant active sites for industrial water splitting.