Oxyanion Engineering Suppressed Iron Segregation in Nickel–Iron Catalysts Toward Stable Water Oxidation

Abstract Nickel–iron catalysts represent an appealing platform for electrocatalytic oxygen evolution reaction (OER) in alkaline media because of their high adjustability in components and activity. However, their long‐term stabilities under high current density still remain unsatisfactory due to undesirable Fe segregation. Herein, a nitrate ion (NO 3 − ) tailored strategy is developed to mitigate Fe segregation, and thereby improve the OER stability of nickel–iron catalyst. X‐ray absorption spectroscopy combined with theoretical calculations indicate that introducing Ni 3 (NO 3 ) 2 (OH) 4 with stable NO 3 − in the lattice is conducive to constructing the stable interface of FeOOH/Ni 3 (NO 3 ) 2 (OH) 4 via the strong interaction between Fe and incorporated NO 3 − . Time of flight secondary ion mass spectrometry and wavelet transformation analysis demonstrate that the NO 3 − tailored nickel–iron catalyst greatly alleviates Fe segregation, exhibiting a considerably enhanced long‐term stability with a six‐fold improvement over FeOOH/Ni(OH) 2 without NO 3 − modification. This work represents a momentous step toward regulating Fe segregation for stabilizing the catalytic performances of nickel–iron catalysts.