Engineering Fe-Nx Sites and Fe2O3 Nanoparticles in N-Doped Porous Carbon as a Durable ORR Catalyst for High-Performance Zinc-Air Batteries

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. Graphical A porous carbazole-based N-doped carbon framework embedded with Fe 2 O 3 nanoparticles and Fe-N x sites was synthesized by pyrolyzing N-rich hypercrosslinked polymers from a Friedel-Crafts reaction, then hemin incorporation. As a Zn-air battery cathode, Fe 2 O 3 /NHCP-2 delivers a power density of 186.84 mW cm −2 , high specific capacity (731.37 mAh g Zn −1 ) and OCV (1.52 V). The porous structure ensures rapid O 2 transport. Fe 2 O 3 nanoparticles and dispersed Fe-N x sites synergistically enhance ORR. This work demonstrates N-rich hypercrosslinked polymers as effective carbon precursors for high-performance ORR catalysts.