Fluorine-engineered Ni3S2/Co9S8 nanorod arrays as high-efficiency OER catalyst for stable seawater electrolysis

The development of high-performance non-precious electrocatalysts for seawater oxidation faces significant challenges from competing chlorine evolution and catalyst corrosion. Herein, we construct fluorine-doped Ni₃S₂/Co₉S₈ nanorod arrays on nickel foam (F-Ni₃S₂/Co₉S₈) as a robust OER catalyst for alkaline seawater electrolysis. Experimental analyses reveal that fluorine doping effectively modulates the electronic structure of Ni/Co active centers, increases catalytically active sites, and enhances charge transfer kinetics, significantly boosting OER activity. Remarkably, F-Ni₃S₂/Co₉S₈ achieves industrially relevant current densities of 1000 mA cm⁻² at low overpotentials of 345 mV (alkaline freshwater) and 407 mV (natural seawater). Importantly, it demonstrates excellent operational stability over 130 h in harsh alkaline seawater conditions, due to its superior chloride corrosion resistance. Furthermore, F-Ni₃S₂/Co₉S₈ exhibits exceptional OER selectivity with a Faradaic efficiency of ∼95 % and no detectable hypochlorite formation. When configured in a full electrolyzer with Pt/C, the system requires only 1.74 V and 1.78 V to deliver 100 mA cm⁻² in freshwater and seawater electrolytes, respectively. This work provides valuable insights into fluorine-mediated catalytic enhancement and presents a promising strategy for developing efficient seawater electrolysis systems.