Size‐Dependent Activity of Iron‐Nickel Oxynitride towards Electrocatalytic Oxygen Evolution

Abstract The exploration of efficient nonprecious metal‐based oxygen evolution reaction (OER) electrocatalysts is of great significance. Herein, both size‐ and component‐tuned FeNi oxynitride are prepared and employed for electrocatalytic water oxidation. Combining the excellent metal‐like feature of induced OER activity of nitrides and oxidation resistance performance of oxides, the obtained FeNi oxynitride delivers an outstanding OER performance. The synergistic interplay between Fe, Ni components creates a favorable local coordination environment for OER and decreased sizes enables more active sites exposure. As a result, under 1 M KOH, the optimized material displays highly efficient electrocatalytic OER performance with low overpotential 295 mV (10 mA cm⁻² catalytic current density) and considerable durability. These findings open up opportunities to explore other excellent catalysts through multicomponent strong interactions coupled with size control.