Electrochemical Reconstruction of Metastable Oxyhalide Realizing a Rechargeable Zn-CO ₂ 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 RBr-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.