Synergistic phase modulation of interstitial Mo and substitutional W single atom in Ni₃S₂ lattice-integrated CoSe heterostructure for industrial water electrolyzers

A rationally engineered non-noble metal catalyst is developed by introducing substitutional tungsten (W, 0.9 wt%) and interstitial molybdenum (Mo, 0.6 wt%) into crystalline nickel sulfide via a synergistic phase-modification strategy. This dual doping induces lattice expansion, structural distortion, and abundant defects in trigonal Ni₃S₂. The modified material is subsequently integrated with cobalt selenide nanowires grown on nickel foam, resulting in the formation of W s /Mo i -Ni₃S₂@CoSe/NF. Atomic-level structural changes are confirmed by scanning transmission electron microscopy and X-ray absorption fine structure analyses. The incorporated conductivity and Mo promotes electron delocalization, shifts the d-band center upward, enhances conductivity, and optimizes intermediate adsorption via Mo (dz²), W (dxz), Ni (dx²-y 2 ), and Co (dx²-y 2 ) orbitals, thereby accelerating hydrogen and oxygen evolution reaction kinetics. The catalyst achieves ultralow overpotentials for the hydrogen evolution reaction (15, 106, 216 mV) and oxygen evolution reaction (200, 295, 350 mV) at current densities of 10, 100, and 1000 mA cm⁻², respectively, in 1.0 M KOH. The assembled electrolyzer operates at just 1.48 V to reach 10 mA cm⁻² and stably delivers 1.0 A cm⁻² for over 1000 h with minimal degradation, surpassing benchmark RuO₂ and Pt/C catalysts. Furthermore, alkaline water electrolysis achieves cell voltages of 1.75 V and 1.88 V at 0.5 and 1.0 A cm⁻² in 6.0 M KOH, highlighting its promise for industrial-scale applications. A study focuses on enhancing the catalytic performance of Ni₃S₂@CoSe heterostructures by synergistic phase-modification strategy incorporates single-atom dopants substitution W s (0.9 wt%) and interstitial Mo i (0.6 wt%) into Ni₃S₂, leading to lattice expansion and structural distortion to maximize active sites. Their synergistic effects improve electronic properties, structural stability, and catalytic efficiency, making the material highly effective for industrial water electrolysis. • W s and Mo i doping induce lattice distortion and defects in Ni₃S₂-CoSe. • Shows ultralow HER/OER overpotentials over wide current densities. • Runs at 1.0 A cm⁻² for 1000 h with minimal degradation in 1.0 M KOH. • Achieves 1.88 V at 1.0 A cm⁻² in 6.0 M KOH, showing practical scalability. • DFT and XAFS reveal orbital interactions optimizing HER and OER kinetics.