In a study published in Angewandte Chemie International Edition, a research team led by Profs. WEN Zhenhai and HUANG Junheng from the Fujian Institute of Research on the Structure of Matter (FJIRSM) of the Chinese Academy of Sciences has developed a fluorine-engineered graphene electrocatalyst with precisely tailored sp²-C-F bonding.

The catalyst enables highly reversible O₂-H₂O₂ interconversion and delivers outstanding performance in zinc-based batteries.

Rechargeable zinc-air batteries (ZABs) are highly promising next-generation energy storage technologies, offering ultrahigh theoretical energy density, intrinsic operational safety and abundant zinc resources. However, their practical deployment has long been hindered by sluggish four-electron (4e^-) oxygen electrocatalysis, including the ORR during discharge and OER during charge. These multistep proton-coupled electron transfers face high energy barriers, leading to large voltage polarization, low round-trip efficiency and accelerated catalyst degradation.

The two-electron (2e^-) O₂-H₂O₂ interconversion pathway has attracted growing attention for its faster intrinsic kinetics and better reversibility. Nevertheless, developing high-performance bifunctional catalysts remains challenging: metal-based catalysts are prone to performance-degrading Fenton-like side reactions, while conventional metal-free carbon catalysts face an inherent conductivity-selectivity trade-off.

In this study, the researchers developed a facile thermal defluorination strategy to synthesize a series of fluorinated graphene (FG-X) with gradient fluorine contents. Using commercial highly fluorinated graphene as the precursor, stepwise pyrolysis under inert atmosphere tunes C‑F bonding from insulating sp³‑C‑F to conductive sp³‑C‑F, while restoring the conjugated sp² carbon network.

The optimized FG‑3 (~3.1 at.% F) achieves an optimal balance between electrical conductivity and catalytic activity, with a well‑recovered graphitic structure, uniform fluorine distribution, high surface area and improved wettability.

Electrochemical evaluations confirmed FG‑3's exceptional bifunctional activity for 2e^-‑ORR and POR, with 97.4% H₂O₂ selectivity and 98.0% Faradaic efficiency. The assembled primary zinc‑oxygen battery delivers a peak power density of 569 mW cm^-2; the rechargeable version realizes a 98.0% round‑trip efficiency at 2 mA cm^-2, retains 97.6% efficiency after 1500 cycles, and operates stably for over 820 hours in ambient air.

Mechanistic studies combining operando spectroscopy and first‑principles simulations revealed that sp²‑C‑F bonds induce localized electrostatic polarization on adjacent carbon sites, stabilizing the key *OOH intermediate and lowering the kinetic barrier.

According to the researchers, this work establishes a clear structure‑property relationship for fluorinated carbon electrocatalysis, offering a general strategy for carbon material engineering and paving the way for durable metal‑air batteries and on‑site H₂O₂ electrosynthesis.

Schematic illustration of the thermal defluorination strategy for synthesizing fluorinated graphene and its application in bifunctional oxygen-peroxide electrocatalysis. (Image by Prof. WEN's group)