Acid-Induced A-Site Regulation of Strontium-Containing Perovskites for Carbonation-Resistant Zn-Air Batteries

Abstract

Under air operation, Sr-containing perovskite cathodes lose activity mainly because the surface Sr species readily react with CO2, rather than because the intrinsic Co/Fe redox centers are insufficiently active. A mild acid treatment was introduced to selectively regulate the surface A-site environment of perovskite oxides, with the aim of suppressing Sr-derived carbonation while retaining the perovskite backbone. The mild acid treatment preferentially regulates Sr-related surface species and partially reconstructs the outermost A-site coordination environment, while the long-range perovskite framework remains largely retained. Such surface A-site modification is accompanied by local charge rebalancing, a shifted electronic state of Co/Fe species, and a higher population of catalytically relevant oxygen-deficient sites, which collectively accelerate oxygen reduction and oxygen evolution reaction kinetics. Benefiting from the reconstructed surface chemistry, the optimized catalyst delivers faster ORR/OER kinetics and, when used in a rechargeable zinc-air battery, affords an open-circuit voltage of 1.50 V, a peak power output of 102.66 mW cm–2, and a discharge capacity of 805 mAh g–1. Under ambient-air operation, the device sustains long-term cycling beyond 300 h, which is consistent with the substantially alleviated carbonate accumulation on the catalyst surface. This work highlights the critical role of A-site chemical stability in designing carbonation-resistant perovskite air cathodes and provides an effective strategy for developing durable bifunctional oxygen electrocatalysts for practical metal-air batteries.