• A low-cost, sustainable synthesis route using cheap flour biomass produces single-atom Fe-N-C catalysts via two-step pyrolysis.
• The catalyst achieves a half-wave potential of 0.86 V, surpassing commercial Pt/C (0.84 V), with superior stability for ORR.
• Atomically dispersed Fe-Nx active sites, high specific surface area (1450.1 m²/g), and abundant micropores enable efficient 4-electron ORR pathway.
• Offers a scalable, cost-effective strategy to balance performance and cost for practical metal-air battery applications.