Robust Amorphous Layer on Fe@Ni Foam for Highly Efficient Alkaline Seawater Oxidation Under High Current Densities

ABSTRACT Developing cost‐efficient and robust anodic electrodes for direct seawater electrolysis that can resist chloride‐induced corrosion remains a significant challenge. In this study, a self‐supporting electrode composed of an amorphous FeNi‐based phosphate layer supported on Fe@Ni foam (AL/Fe@Ni) was successfully fabricated via a facile in situ hydrothermal growth method. During the oxygen evolution reaction (OER), the amorphous layer undergoes in situ reconstruction accompanied by the dissolution of phosphate anions, leading to the formation of Fe‐doped Ni(oxy)hydroxide nanosheets. In situ Raman spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy analyses demonstrate that Fe‐ion doping plays a critical role in promoting this reconstruction process. Quantitative analysis of element dissolution and chloride adsorption reveals that the dynamic desorption and re‐adsorption of leached phosphate anions provide the electrode with electrostatic repulsion against chloride ions. Moreover, the redeposition of a small amount of dissolved Fe ions suppresses the dissolution of active elements, establishing a self‐healing mechanism. Theoretical calculations further reveal that the dissociated PO 4 3− anions preferentially adsorb onto the surface of the reconstructed Ni(Fe)OOH, promoting more favorable adsorption of OH − compared to Cl − due to strong repulsive interactions between anchored PO 4 3− and Cl − . Benefiting from the integrated effects, including the reconstructed highly active phase, suppressed chlorine evolution reaction, self‐healing capability, enhanced mass transfer endowed by superhydrophilic and superaerophobic properties, and inherent anticorrosion behavior, the electrode exhibits high OER selectivity and exceptional durability. This work offers a new perspective for designing and fabricating highly efficient and robust electrodes for seawater electrolysis.