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 <200 mA cm −2 , far lower than industrially‐required 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 Mo 2 S 3 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 H 2 generation. The Mo 2 S 3 @NiMo 3 S 4 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 RuO 2 ||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.