Ultrafast\nRoom-Temperature Synthesis of Phosphate-Intercalated\nNiFe Layered Double Hydroxides for High-Performance Alkaline Seawater\nOxidation

Quick and easy synthetic methods and highly efficient\ncatalytic\nperformance are equally important to anodic oxygen evolution reaction\n(OER) electrocatalysts for alkaline seawater electrolysis. Herein,\nwe report a facile one-step route to in situ growing PO<sub>4</sub><sup>3–</sup> intercalated NiFe layered double hydroxides\n(NiFe-LDH) on Ni foam (denoted as NiFe-P/NF) by a room-temperature\nimmersion for several minutes. This ultrafast approach transforms\nthe NF surface into a rough PO<sub>4</sub><sup>3–</sup> intercalated\nNiFe-LDH overlayer, which demonstrates outstanding OER performance\nin both alkaline simulated and natural seawaters owing to good hydrophilic\ninterface and the electrostatic repulsion of PO<sub>4</sub><sup>3–</sup> against Cl<sup>–</sup> anions. Density functional theory\ncalculations reveal that the intercalated PO<sub>4</sub><sup>3–</sup> can not only promote electron transfer but also prevent Cl<sup>–</sup> from entering the interlayer and simultaneously inhibit the migration\nof Cl<sup>–</sup> over the NiFe-LDH surface. In alkaline simulated\nand natural seawater electrolytes, NiFe-P/NF needs low overpotentials\nof 248 and 298 mV to achieve a current density of 100 mA cm<sup>–2</sup>, respectively. NiFe-P/NF can stably run over 42 h in an alkaline\nhigh-salty electrolyte (1 M KOH + 2.5 M NaCl) at 250 mA cm<sup>–2</sup>, more than 70 times that of NiFe/NF (0.6 h), emphasizing the critical\nrole of the intercalated PO<sub>4</sub><sup>3–</sup> anions\non the excellent durability. This study offers a new strategy to modify\ncommercial NF to prepare efficient and stable OER catalysts for seawater\nelectrolysis.