A ball-milling assisted pyrolysis strategy is developed to synthesize atomically metal dispersed Fe–N–C/Gra-600 with Fe-N _x sites, achieving superior ORR and OER performance beyond commercial Pt/C. The catalyst shows enhanced OER activity under high electrolyte concentration due to increased active surface area and optimized electron transfer, enabling a Zn–air battery with 430 mW cm⁻² peak power density and stable cycling. This bifunctional excellence stems from the Fe–N _x species synergistically with high conductive property of graphene.

Abstract

Developing nonprecious metal oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts with both high activity and stability remains a critical challenge for advanced metal–air battery. In this work, we develop a ball-milling assisted pyrolysis strategy to fabricate atomically dispersed Fe anchored on nitrogen-doped graphene (Fe–N–C/Gra), which precisely constructs Fe-N _x active centers for efficient ORR/OER bifunctional catalysis. The fabricated Fe–N–C/Gra-600 demonstrates ORR half-wave potential of 0.862 V and OER overpotential of 1.743 V at 10 mA cm⁻², surpassing commercial Pt/C benchmarks. Remarkably, under high electrolyte concentration conditions, catalyst exhibits reduced OER overpotentials due to increased electrochemical active surface area and optimized electron transfer resistance. Noteworthy, the Zn–air battery equipped with Fe–N–C/Gra-600 as air electrode catalyst, delivers a remarkable peak power density of 430 mW cm⁻², along with excellent charge–discharge cycling stability at 10 mA cm⁻². The outstanding bifunctional performance originates from synergistic effects of Fe–N–C/Gra-600, in which atomically dispersed Fe accelerates adsorption and activation of reactants due to formation of Fe–N _x species, synergistically with high conductive property of graphene substrate. This study not only demonstrates great potential of graphene-supported Fe–N–C single-atom catalysts for metal–air battery applications but also provides a new strategy for preparing high-performance nonprecious metal electrocatalysts.