LAUSR

Alkaline water electrolysis is commercially desirable to realize large‐scale hydrogen production. Although nonprecious catalysts exhibit high electrocatalytic activity at low current density (10–50 mA cm−2), it is still challenging to achieve industrially required current density over 500 mA cm−2 due to inefficient electron transport and competitive adsorption between hydroxyl and water. Herein, the authors design a novel metallic heterostructure based on nickel nitride and monoclinic molybdenum disulfide (Ni3N@2M‐MoS2) for extraordinary water electrolysis. The Ni3N@2M‐MoS2 composite with heterointerface provides two kinds of separated reaction sites to overcome the steric hindrance of competitive hydroxyl/water adsorption. The kinetically decoupled hydroxyl/water adsorption/dissociation and metallic conductivity of Ni3N@2M‐MoS2 enable hydrogen production from Ni3N and oxygen evolution from the heterointerface at large current density. The metallic heterostructure is proved to be imperative for the stabilization and activation of Ni3N@2M‐MoS2, which can efficiently regulate the active electronic states of Ni/N atoms around the Fermi‐level through the charge transfer between the active atoms of Ni3N and MoMo bonds of 2M‐MoS2 to boost overall water splitting. The Ni3N@2M‐MoS2 incorporated water electrolyzer requires ultralow cell voltage of 1.644 V@1000 mA cm−2 with ≈100% retention over 300 h, far exceeding the commercial Pt/C║RuO2 (2.41 V@1000 mA cm−2, 100 h, 58.2%).