Engineering Fe‐N _x Sites and Fe ₂ O ₃ Nanoparticles in N‐Doped Porous Carbon as a Durable ORR Cat

ABSTRACT

The development of efficient and durable non‐precious metal electrocatalysts for the oxygen reduction reaction (ORR) is critical to advancing electrochemical energy devices. Herein, we report a porous, carbazole‐based N‐doped carbon framework catalyst embedded with Fe ₂ O ₃ nanoparticles and Fe‐N _x sites. The catalyst was synthesized via pyrolysis of N‐rich hypercrosslinked polymers (NHCP), which were derived from the Friedel‐Crafts reaction, followed by incorporation of hemin (Fe ₂ O ₃ /NHCP‐2). The introduction of hemin not only preserved the pristine porous architecture but also facilitated the formation of Fe ₂ O ₃ nanoparticles and Fe‐N _x sites, and their synergistic effect enhanced the ORR kinetics in alkaline media. The optimized Fe ₂ O ₃ /NHCP‐2 catalyst exhibited a high half‐wave potential of 0.87 V and demonstrated robust long‐term durability in a 0.1 M KOH solution. When employed as the cathode material in zinc‐air batteries (ZABs), it delivered a peak power density of 186.84 mW cm ⁻² and a specific capacity of 731.37 mAh g _Zn ⁻¹ . This study presents a promising non‐precious metal ORR electrocatalyst for future renewable energy applications.