Formation of HO 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 HO-mediated pathway facilitates oxygen evolution reaction (OER) at ~1.5 V vs. Zn/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 ZnSO solutions and carbon nanotubes. Enhancing the HO-mediated pathway offers a route to higher energy efficiency and durability in near-neutral ZABs, advancing practical, sustainable energy storage.