Promoting nickel oxidation state transformation in NiFe hydroxide nanosheets for efficient oxygen evolution reaction

Promoting the formation of high oxidation state transition metal species in hydroxide catalysts can enhance their catalytic activity for the oxygen evolution reaction (OER). In this work, we present a method for synthesizing NiFe hydroxide nanosheets under ambient temperature and pressure, and demonstrate the efficacy of high oxidation state Ni in boosting OER activity. In situ Raman spectroscopy indicates that active Ni^3+δOOH species are formed in the NiFe hydroxide nanosheets. Consequently, a current density of 10 mA cm^-2 is achieved at a low overpotential of 222 mV in 1 M KOH, with remarkable stability exceeding 2000 hours at 10 mA cm^-2, which ranks it among the superior Ni-based OER catalysts. This work provides a novel approach for the synthesis of metal hydroxides, promising gram-scale and beyond production of electrocatalytic materials for efficient oxygen evolution reaction in water splitting.