Phosphate‐Modified NiFe Catalyst for Efficient and Robust Alkaline Water and Seawater Oxidation

ABSTRACT To achieve sustainable hydrogen production through seawater electrolysis, it is essential to develop efficient and stable electrocatalysts for the oxygen evolution reaction (OER). Herein, we develop a high‐performance phosphate‐modified nickel‐iron catalyst directly on iron foam (FeNiPi/FF) via a facile and scalable two‐step strategy, which integrates anodic electrodeposition and subsequent in situ soaking. Systematic structural characterization reveals that the optimized catalyst possesses a unique hierarchical nanoflower architecture, which confers a substantially increased electrochemical surface area. Furthermore, it is enriched with electrochemically active high‐valence Ni ³⁺ /Fe ³⁺ species and stabilized by strongly incorporated phosphate anions. This synergistic configuration enables the FeNiPi/FF electrode to demonstrate superior OER activity and robust durability in alkaline water and seawater. It requires low overpotentials of merely 320 and 346 mV to deliver a high current density of 500 mA cm ^{− 2} in alkaline water and alkaline seawater electrolytes, respectively, and maintains superb long‐term operational stability. This work not only provides a practical and effective pathway for designing non‐precious metal catalysts with enhanced activity and corrosion resistance but also advances the development of efficient alkaline water and alkaline seawater splitting systems for a green hydrogen economy.