Constructing amorphous/crystalline NiFe-MOF@NiS heterojunction catalysts for enhanced water/seawater oxidation at large current density

Developing metal-organic frameworks (MOF) based catalysts with high activity and chlorine corrosion resistance is of paramount importance for seawater oxidation at large current density. Herein, we report a heterogeneous structure coupling NiFe-MOF nanoparticles with NiS nanosheets onto Ni foam (denoted as the NiFe-MOF@NiS/NF) via the mild strategy involving sulfur-modified corrosion and electrodeposition treatment. The constructed amorphous/crystalline interfaces could not only facilitate the adequate infiltration of electrolyte and release of O₂ bubbles at large current densities, but also significantly improve the charge transfer from NiFe-MOF to NiS and the adsorption/desorption capacity of oxygen intermediates. Intriguingly, during oxygen evolution reaction process, the sulfate film formed by the self-reconstruction could remarkably inhibit the adsorption of Cl^– ions on the catalyst surface in the seawater electrolytes. Benefiting from the robust corrosion resistance, unique amorphous/crystalline interfaces, and the charge redistribution, the well-designed NiFe-MOF@NiS/NF exhibits the low overpotential of 346 and 355 mV under a high current density of 500 mA cm⁻² in alkaline water and seawater electrolytes, respectively. More importantly, the as-fabricated NiFe-MOF@NiS/NF demonstrates prolonged stability and durability, lasting over 600 h at a current density of 100 mA cm⁻² in both electrolytes. This study enriches the understanding of electronic structure modulation and chlorine corrosion resistance in seawater, providing broad prospects for designing advanced MOF-based catalysts.