Boosted Alkaline Oxygen Evolution Reaction via Phosphorus Incorporation in FeCoS2@MoS2 Core-Shell Heterostructures

Achieving sustainable energy conversion hinges on the rational design of oxygen evolution reaction (OER) electrocatalysts that deliver both high efficiency and low cost. Herein, we report a phosphorus-doped iron-cobalt sulfide/molybdenum sulfide heterostructure on nickel foam (P-FeCoS2@MoS2/NF) as an effective OER electrocatalyst in both alkaline freshwater and alkaline seawater. During the sulfurization and phosphorization steps, MoS2 nanosheets are vertically grown on the surface of FeCoS2 nanorods derived from FeCo-layered double hydroxide, forming a heteroatom-P doped core-shell architecture. The core-shell structure prevents the restacking of MoS2 nanosheets and exposes an abundant active surface. The heterointerface induces strong electronic coupling and boosts the active sites to improve the catalytic performance. Experimental characterization confirms the successful formation of the heterostructure and the uniform distribution of phosphorus. Owing to the synergistic effects of a hierarchical structure, the formation of heterointerfaces, and phosphorus doping, P-FeCoS2@MoS2/NF exhibits exceptional OER activity, requiring overpotentials of 220 and 226 mV to reach 10 mA cm-2 in the alkaline electrolyte and alkaline seawater electrolyte, respectively, together with excellent catalytic stability. The low Tafel slope and diminished interfacial charge-transfer resistance in both electrolytes elucidate the rapid reaction kinetics during the OER operation. Post-OER analysis demonstrates the preserved morphology and surface chemistry, underscoring its structural robustness. This work offers a multi-step compositional and structural engineering approach for designing advanced metal sulfide-based heterostructure electrocatalysts for hydrogen production.