Hybrid Nano-Atomic IrFe-N-C for Low-Iridium Oxygen Electrocatalysis

Designing efficient bifunctional catalysts for oxygen evolution and oxygen reduction reactions (OER/ORR) is essential for advancing metal-air batteries, yet remains challenging due to the fundamentally distinct reaction pathways involved. Here, we address this challenge by developing a hybrid IrFe-N-C electrocatalyst that integrates IrFe nanoparticles with a Fe-N-C support rich in atomically dispersed Fe-N₄ sites. This hierarchical active-site design enables functional complementarity: IrFe nanoparticles preferentially catalyze the OER, while Fe-N₄ moieties serve as highly active ORR sites. Effective metal-support interactions stabilize both single atoms and ultrafine nanoparticles, ensuring high activity and stability. As a result, the catalyst exhibits impressive bifunctional performance with reduced Ir loading, achieving an OER overpotential of only 227 mV at 10 mA cm^-2. The mass activities for both OER and ORR far surpass those of state-of-the-art Ir/C and Pt/C benchmarks. When implemented in Zn-air batteries, the catalyst delivers promising power density and fair cycling stability. These results establish a rational design strategy for cost-effective, durable bifunctional catalysts toward next-generation energy storage technologies.