Potassium fluoride-induced FeOOH formation in NiFe oxalate for improved oxygen evolution performance.

Our study introduces a facile synthetic route for the in situ formation of nickel (Ni)-iron (Fe) oxyhydroxide from NiFe oxalate. By adding potassium fluoride (KF) to the synthetic solution, we achieved a predominant surface distribution of Fe (>80 at%) while limiting its bulk incorporation compared to solutions without KF. Operando Raman spectroscopy analysis confirms that the enriched Fe predominantly exists as FeOOH. Our optimized catalyst demonstrates significant efficiency, achieving a current density of 10 mA cm-2 at a notably low overpotential of 226 mV.