Interface Engineering of Trace Fe ₃ O ₄ /NiO on Ultra‐Thin Carbon‐Nitride for Enhanced Electrocatalytic Oxygen Evolution

Transition metal oxides (TMOs) are promising alternatives to precious‐metal electrocatalysts for the oxygen evolution reaction (OER), but their low intrinsic activity and high overpotentials present a critical challenge. Therefore, how to improve the intrinsic activity of TMO remains a challenge. Herein, Fe 3 O 4 /NiO heterointerfaces were constructed on ultra‐thin carbon nitride substrates via interface engineering, yielding a hybrid catalyst denoted as Fe 3 O 4 /NiO@CN‐1 for alkaline oxygen evolution reaction (OER). ICP analysis results show that the metal loading is extremely low, with 0.20 wt% Fe and 0.33 wt% Ni. Benefiting from interfacial coupling and charge‐transfer/adsorption behavior, Fe 3 O 4 /NiO@CN‐1 exhibits a better OER performance with an overpotential of 305.73 mV at the current density of 10 mA cm −2 and a current density of 124.7 mA cm −2 in 1 M KOH. Despite the trace metal content, its activity possesses certain competitiveness among non‐precious‐metal catalysts, highlighting the key role of Fe 3 O 4 /NiO heterointerfaces on ultra‐thin CN. The LSV curve remains nearly unchanged after 1000 cyclic voltammetry scans and stable operation is maintained for ≥22 h, suggesting promising stability under laboratory conditions. This study provides a feasible strategy to develop high‐performance non‐precious‐metal OER catalysts on CN supports via heterointerface engineering with minimized transition‐metal usage.