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• Metallic Ni 3 Mo 3 N porous microrods showed a low overpotential of 44.6 mV to attain a current density of 10 mA cm−2 and superstability at a large current density of 1100 mA cm−2 for 50 h. • Density functional theory (DFT) calculations clarified that the Ni 3 Mo 3 N electrocatalyst possesses various HER catalytic active sites with suitable ΔG H* values (more than ten sites) due to the metallic semiconductor structure with special electronic structure. • The constructed NC/Ni 3 Mo 3 N/NF||NiMoO 4 ·xH 2 O/NF only needed a voltage of 1.58 V to attain a current density of 50 mA cm−2, which was better than that of 20 wt% Pt/C||RuO 2 (1.71 V), and has high potential for large-scale industrial applications. The low onset potential and large current density of electrocatalysts has always been important target for hydrogen evolution reaction (HER). In especial, the large current density (larger than 1000 mA cm−2) is an important criterion for the evaluation of electrocatalysts for industrial application. Usually, the number of catalytic sites in electrocatalyst limits the current density for HER. To overcome these problems, bimetallic nitride is controllably synthesized, and the corresponding catalytic sites are regulated by a bimetallic effect. Herein, an inexpensive electrocatalyst consisting of N-doped carbon-coated porous Ni 3 Mo 3 N microrods (NC/Ni 3 Mo 3 N/NF) is cultured on nickel foam using a hydrothermal reaction and subsequent nitriding process. The designed electrocatalyst consisting of porous NC/Ni 3 Mo 3 N microrods displays efficient catalytic activity for hydrogen evolution reaction (HER), with a small overpotential of 136 mV to achieve a cathodic current density of 100 mA cm−2. Density functional theory (DFT) calculations clarified that the Ni 3 Mo 3 N electrocatalyst possesses various HER catalytic active sites with suitable ΔG H* values (more than ten sites) due to the metallic semiconductor structure with special electronic structure. It is important that NC/Ni 3 Mo 3 N/NF possess perfect superstability for HER, with a large current density of 1100 mA cm−2 for 50 h. Lastly, NC/Ni 3 Mo 3 N/NF and NiMoO 4 ·xH 2 O/NF are hired as the cathode and anode, respectively, to assemble the two-electrode electrolytic cell, thereby achieving excellent overall water splitting performance with a voltage of 1.58 V at 50 mA cm−2 in 1 M KOH aqueous solution. [ABSTRACT FROM AUTHOR]