Self‐Adapting Oxyanion Armor Achieves Highly Stable and Efficient Seawater Electrolysis at Ampere‐Level Current Densities

Abstract Seawater electrolysis is an effective way for large‐scale green hydrogen. Nevertheless, the anode suffers from the severe corrosion of Cl − and Br − during oxygen evolution, which gives rise to the issues of narrow‐deep pits and shallow‐wide pits, respectively. Herein, an anti‐corrosion strategy is presented by self‐adapting oxyanion armor to prevent the high valence active sites from Cl − and Br − corrosion. The core–shell FeNi 2 Se 4 @NiFe‐Phy is reconstructed to active species NiFeOOH covered by an oxyanion layer composed of phosphoric and carbonate. The aimed anode exhibits remarkable efficiency, achieving current densities of 10 and 200 mA cm −2 at overpotentials of merely 220 and 277 mV, respectively. Notably, it shows unparalleled durability, enduring without any discernible degradation following rigorous testing for 400 h at 400–1000 mA cm −2 in alkaline simulated seawater, as well as natural seawater. A combination of density functional theory calculations and molecular dynamics simulations further confirms the bifunctional enhancement of oxyanion armor on NiFeOOH surface. At a current density of 200 mA cm −2 , the alkaline seawater electrolyzer has significant energy efficiency, consuming merely 4.61 and 4.27 kWh Nm −3 H 2 at room temperature and 80 °C, respectively. This work offers an efficacious surface corrosion resistance strategy for anode protection during seawater electrolysis.