Dual-Anion Regulation for Reversible and Energetic Aqueous Zn-CO₂ Batteries

Aqueous Zn-CO₂ batteries can not only convert CO₂ into high-value chemicals but also store/output electric energy for external use. However, their performance is limited by sluggish and complicated CO₂ electroreduction at the cathode. Herein, a dual-anion regulated Bi electrocatalyst is developed to selectively reduce CO₂ to formate with a Faradaic efficiency of up to 97% at a large current density of 250 mA cm^-2. With O and/or F, the rate-determine step of CO₂ electroreduction has been manipulated (from the first hydrogenation to *HCOOH desorption step) with a reduced energy barrier. Significantly, the fabricated Zn-CO₂ battery exhibits a high discharge voltage of 1.2 V, optimal power density of 4.51 mW cm^-2, remarkable energy density of 802 Wh kg^-1, and energy-conversion efficiency of 70.74%, stability up to 200 cycles and 68 h. This study provides possible strategies to fabricate reversible and energetic aqueous Zn-CO₂ batteries by addressing cathodic problems.