Engineering P-Fe₂O₃-CoP nanosheets for overall freshwater and seawater splitting

Tailoring surface composition and coordinative environment of catalysts in a nano-meter region often influence their chemical performance. It is reported that CoP exhibits a low dissociation ability of H-OH, originating from the poor desorption of intermediate species. Herein, we provide a feasible method to construct P-Fe₂O₃-CoP nanosheets through a gas-phase phosphorization process. P doping induces the formation of interfacial structure between Fe₂O₃ and CoP and the generation of defective structures. The resulting P-Fe₂O₃-CoP nanosheets afford high freshwater/seawater oxidation activity (250/270 mV@10 mA/cm²) in 1 mol/L (M) KOH, which is even lower than commercial RuO₂. Compared with CoP||CoP, P-Fe₂O₃||P-Fe₂O₃, and Co₃O₄||Co₃O₄, the assembled P-Fe₂O₃-CoP||P-Fe₂O₃-CoP exhibits the superior water/seawater electrolysis performance with 1.61/1.65 V@10 mA/cm². The synergistic effect of P doping, defective structure, and heterojunction leads to high water oxidation efficiency and water splitting efficiency.