Reconstruction‐Induced Bilayered Amorphous–Crystalline Hybrid NiOOH‐Based Anode for Ultrastable Seawater Electrolysis

ABSTRACT Direct seawater electrolysis represents a critical pathway for large‐scale utilization of renewable energy in coastal and island regions without potential impacts on freshwater supply, yet being severely hindered by the corrosion of electrode materials in seawater. Conventional anion‐based protection strategies often suffer from lattice degradation during activation or anion desorption in operation. Herein, we report a facile electrodeposition‐anodization synthesized amorphous–crystalline hybrid NiFeCoCr anode featuring a vertically bilayered architecture, enabling ultrastable seawater oxidation for over 15 000 h at 500 mA cm −2 . During anodization, the partial sacrificial leaching of Cr forms an amorphous β‐NiOOH phase surface layer, exposing abundant active sites to enhance OER activity. Concurrently, in situ generated CrO 4 2– anions stably adsorb and intercalate within the dense crystalline Fe/Co‐doped γ‐NiOOH underneath layer. The electrolyzer assembled with the NiFeCoCr anode delivers stable operation for over 2500 h in alkaline natural seawater and for 240 h in alkaline saturated NaCl electrolyte at 80°C.