Formation of H₂O₂ in Near-Neutral Zn-air Batteries Enables Efficient Oxygen Evolution Reaction

Rechargeable Zn-air batteries (ZABs) with near-neutral electrolytes hold promise as cheap, safe and sustainable devices, but they suffer from slow charge kinetics and remain poorly studied. Here we reveal a charge storage mechanism of near-neutral Zn-air batteries that is mediated by formation of dissolved hydrogen peroxide upon cell discharge and its oxidation upon charge. This H₂O₂-mediated pathway facilitates oxygen evolution reaction (OER) at ~1.5 V vs. Zn²⁺/Zn, reducing charge overpotentials by ~0.2–0.5 V and mitigating carbon corrosion—a common issue in ZABs. The manifestation of this mechanism strongly depends on the electrolyte composition and positive electrode material, contributing up to ~60 % of the capacity with ZnSO₄ solutions and carbon nanotubes. Enhancing the H₂O₂-mediated pathway offers a route to higher energy efficiency and durability in near-neutral ZABs, advancing practical, sustainable energy storage.