N-doping site modulation via in situ atomic substitution enables high round-trip efficiency H2O2-mediated Zn-oxygen batteries

While noble metal-based catalysts remain the most effective for the four-electron oxygen reduction reaction (ORR), nitrogen-doped carbon materials are promising non-metal alternatives. However, atomic-level modulation of pyridinic-N sites to rival Pt-based ORR activity remains a fundamental challenge. To address this, we developed a novel “defect-guided in situ atomic substitution” strategy. Using highly fluorinated graphene as a precursor, we achieved synchronous defluorination, graphitization, and precise nitrogen doping through a one-step thermochemical process. C F bond cleavage generates transient carbon vacancies that serve as anchoring sites, constructing a catalytic surface rich in pyridinic nitrogen. The resulting nitrogen-doped graphene catalyst (PN-G) exhibits outstanding bifunctional activity: for ORR, it achieves a half-wave potential of 0.86 V and an average electron transfer number of ∼3.90; for the hydrogen peroxide oxidation reaction (HPOR), its onset potential is reduced by over 0.5 V compared to the oxygen evolution reaction (OER). In situ Raman identified *O 2 − as a central role in bidirectional oxygen electrocatalysis (ORR and HPOR). Utilizing PN-G catalyst, we constructed a rechargeable zinc‑oxygen battery employing an H 2 O 2 -mediated electrolyte. This battery delivers a peak power density of 710 mW cm −2 and a round-trip energy efficiency of ∼96% at 5 mA cm −2 . This work not only establishes a controllable synthetic route for high-performance metal-free carbon catalysts but also provides a practical approach for designing efficient metal-air batteries.