Ultrafast Room-Temperature Synthesis of Phosphate-Intercalated NiFe Layered Double Hydroxides for High-Performance Alkaline Seawater Oxidation

Quick and easy synthetic methods and highly efficient catalytic performance are equally important to anodic oxygen evolution reaction (OER) electrocatalysts for alkaline seawater electrolysis. Herein, we report a facile one-step route to in situ growing PO₄^3- intercalated NiFe layered double hydroxides (NiFe-LDH) on Ni foam (denoted as NiFe-P/NF) by a room-temperature immersion for several minutes. This ultrafast approach transforms the NF surface into a rough PO₄^3- intercalated NiFe-LDH overlayer, which demonstrates outstanding OER performance in both alkaline simulated and natural seawaters owing to good hydrophilic interface and the electrostatic repulsion of PO₄^3- against Cl^- anions. Density functional theory calculations reveal that the intercalated PO₄^3- can not only promote electron transfer but also prevent Cl^- from entering the interlayer and simultaneously inhibit the migration of Cl^- over the NiFe-LDH surface. In alkaline simulated and natural seawater electrolytes, NiFe-P/NF needs low overpotentials of 248 and 298 mV to achieve a current density of 100 mA cm^-2, respectively. NiFe-P/NF can stably run over 42 h in an alkaline high-salty electrolyte (1 M KOH + 2.5 M NaCl) at 250 mA cm^-2, more than 70 times that of NiFe/NF (0.6 h), emphasizing the critical role of the intercalated PO₄^3- anions on the excellent durability. This study offers a new strategy to modify commercial NF to prepare efficient and stable OER catalysts for seawater electrolysis.