Rational design of Mo-doped NixSy/Ni2P heterostructure on nickel foam for high-efficiency hydrogen evolution in alkaline freshwater and seawater media

The development of highly active and long-lasting multifunctional electrocatalysts is crucial for advancing clean and renewable energy technologies. In this study, we developed a Mo-doped Ni_xS_y/Ni₂P self-supported electrode anchored on nickel foam (Mo-Ni_xS_y/Ni₂P/NF) through a sequential hydrothermal reaction and calcination-phosphating strategy. The optimized Mo-Ni_xS_y/Ni₂P/NF demonstrates outstanding electrocatalytic activity for the hydrogen evolution reaction (HER) in both alkaline freshwater and simulated seawater environment. Electrochemical characterization reveals that the optimal Mo-Ni_xS_y/Ni₂P/NF catalyst requires remarkably low overpotentials of 77 mV (alkaline freshwater) and 110 mV (alkaline simulated seawater) to achieve 10 mA cm⁻², accompanied by Tafel slopes of 92.24 and 112.66 mV dec⁻¹, respectively. Notably, the electrocatalyst exhibits exceptional operational stability, maintaining performance integrity for 200 h at 100 mA cm⁻² current density. Material characterization demonstrates that Mo doping induces structural modification of Ni₃S₂ while facilitating the formation of Ni₉S₈ phases, synergistically enhancing the catalytic architecture. Subsequent phosphating treatment further stabilizes the electrode morphology and improves interfacial charge transfer characteristics. Comparative analysis confirms the superior catalytic efficiency of Mo-Ni_xS_y/Ni₂P/NF over conventional HER catalysts in both aqueous environments. This work provides a reasonable and feasible approach for designing highly efficient electrocatalysts.