Synthesis of crystalline/amorphous NiMn2O4/CoSx heterointerface for efficient and durable alkaline water/seawater electrolysis

In seawater electrolysis, the presence of Cl − ions corrodes the electrode and causes side reactions, severely degrading OER efficiency and stability. To address these challenges, we developed a crystalline-amorphous heterointerface to enhance their OER activity and stability. The synergistic coupling of crystalline and amorphous phases creates optimal sites for superior catalytic activity. In addition to the robust performance, partial leaching of the amorphous CoS x phase forms a protective sulfate layer and triggers surface reconstruction. This rich passivated layer of OH − creates an alkaline environment near the electrode surface that repels Cl − electrostatically. Therefore, the optimum NiMn 2 O 4 /CoS x catalyst indicates an ultralow overpotential of 220 and 255 mV at 100 mA cm −2 and robust performance of 700 h and 300 h at 500 mA cm −2 in alkaline and seawater conditions. This work provides a blueprint for developing highly effective and stable catalysts for clean energy production.