Ni₃S₂/NiFe-MOF heterostructure for efficient water/seawater oxidation

The development of efficient and corrosion-resistant electrocatalysts is critical for advancing seawater electrolysis as a sustainable hydrogen production strategy. Here, we report a partial sulphuration method to construct a Ni₃S₂/NiFe-btz heterostructure (btz: 1,4-bis(4H-1,2,4-triazol-4-yl)benzene), optimized by tuning the hydrothermal duration. This unique structure affords sufficient metal-organic framework (MOF)/sulfide interfaces, providing numerous active sites, optimized electronic configurations, and rapid charge transfer. Theoretical calculations confirm that the heterostructure lowers the energy barrier of the rate-determining step, improving oxygenated species adsorption and intrinsic activity. Moreover, water oxidation induces a protective sulfate layer, effectively mitigating chloride corrosion and ensuring long-term stability in natural seawater electrolysis. As a result, the optimized Ni₃S₂/NiFe-btz requires an overpotential of 359 mV to reach 500 mA cm^-2 in alkaline natural seawater, which is much lower than that of 447 mV for single-phase NiFe-btz. In addition, it demonstrates remarkable durability, maintaining stable operation for over 200 h at 500 mA cm^-2 with minimal overpotential increase. This work offers insight into designing high-performance oxygen evolution reaction electrocatalysts for industrial seawater electrolysis.