Electrochemical Reconstruction of Metastable Oxyhalide Realizing a Rechargeable Zn-CO₂ Battery

Bismuth-based catalysts are highly promising for the CO₂ reduction reaction (CO₂RR) because of their outstanding catalytic performance. However, precise engineering of the surface-interface electronic architecture in these catalysts to refine CO₂ adsorption and activation remains a critical hurdle. Herein, we synthesize various metastable oxyhalides, followed by in situ electrochemical reconstruction to form Bi₂O₂CO₃/Bi₂O₃ heterostructures with carbonate-bismuth-oxygen (CO₃-Bi-O) heterosites. In situ and ex situ measurements and theoretical studies reveal that in these CO₃-Bi-O heterosites electron accumulation in Bi zones and depletion in O regions create a localized interfacial dipole effect, promoting favorable CO₂ adsorption and activation. The resulting heterosites enhance CO₂RR selectivity to formate (92.5%), with a 12.5% improvement at -1.2 V (vs RHE) over pure Bi₂O₃. The superiority of BiOBr-derived R_Br-Bi₂O₂CO₃/Bi₂O₃ is demonstrated in a proof-of-concept Zn-CO₂ battery, yielding twice the power density of Bi₂O₃-derived l-Bi₂O₂CO₃/Bi₂O₃. This work paves the way for electrochemical reconstruction strategies in novel CO₂-based battery exploration.