Abstract: Seawater is abundant in nature, and its application as a raw material for hydrogen production by electrolysis has a broad prospect. However, the presence of chloride ions (Cl⁻) in the electrolysis process triggers chlorination evolution reaction (CER) side-reaction competition and anode material corrosion, which seriously restricts the development of seawater electrolysis technology. To address this dilemma, the development of oxygen volution reaction (OER) electrode materials with excellent catalytic activity, chlorine corrosion resistance properties, and low cost has become the focus of current research. In this study, a Co₂P/NF electrode was rapidly synthesized on a nickel foam substrate in a few minutes by electrodeposition. The electrode exhibits excellent OER performance (286 m @100 mA/cm²) and excellent long-term stability (Only 2.7% weakness in 100 h) in alkaline seawater environment. This is attributed to the repulsive effect of PO₄³⁻ generated by CV activation on Cl⁻ in seawater, thereby extending the service life of the electrode.