Simultaneous Promotion of Lattice Oxygen Mechanism and Chloride Resistance via Iron Doping in Cobalt Sulfide toward Robust Seawater Splitting

Abstract

Triggering the lattice oxygen oxidation mechanism is crucial for enhancing oxygen evolution reaction (OER) performance; yet effectively boosting lattice oxygen participation and stability remains a challenge. Herein, iron-doped cobalt sulfides (Fe-CoSx) on carbon cloth are successfully synthesized via a one-step electrodeposition method. The optimal CoFe0.16Sx electrocatalyst exhibits remarkable OER performance, requiring overpotentials of only 220 and 300 mV to achieve 100 and 500 mA cm⁻2 in alkaline seawater, respectively, along with outstanding stability for over 125 h. Comprehensive characterization reveals that Fe doping serves multiple critical functions: (i) it significantly strengthens the adsorption of hydroxide ions (OH⁻), accelerates the in situ reconstruction of the catalyst surface and facilitates the deep oxidation of CoOOH to CoO2, thereby promoting a more efficient LOM pathway; and (ii) it stabilizes sulfate ions on the reconstructed surface, forming a protective layer that electrostatically repels chloride ions. These endow the catalyst with superior corrosion resistance and stable OER activity in chloride-containing alkaline electrolytes. This work provides an effective multifunctional doping strategy and mechanistic insights for the design of high-performance, stable OER electrocatalysts.