Reasonable construction of the electrocatalyst for oxygen evolution reaction (OER) with earth abundant elements, strong corrosion resistance and high catalytic activity is of great significance to the seawater splitting and hydrogen energy developing. In this work, an amorphous/crystalline phase (a-c) heterogeneous interface (FeMoP/Ni3S2) is designed, synergizing with an in-situ dynamically restructured dual Cl⁻- repelling layers to achieve long-term and ultrastable operation in seawater oxidation. The dual Cl⁻- repelling layers (PO43-/SO42-) effectively repel Cl⁻ through electrostatic attraction, reduce the adsorption energy of Cl⁻ on the interface, further promoting its preeminent corrosion resistance under harsh marine conditions. The built-in electric field formed at the a-c interface modulates the electronic structure and reduces the energy barrier required for the rate-determining (*O →*OOH), greatly beneficial for accelerating the kinetics process of 4 e- oxygen evolution reaction (OER), endowing it with excellent electrocatalytic OER performance. Benefit from the above ingenious design, FeMoP/Ni3S2 only needs a low overpotential of 308 mV to reach a current density of 100 mA cm-2, achieving excellent long-term durability for 300 hours at 500 mA cm-2 in alkaline seawater. A promising strategy has therefore been provided for developing high-efficiency and corrosion-resistant seawater electrocatalysts, well contributing to the development of hydrogen energy in the future.
