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

Bismuth-based catalysts are highly promising for the CO 2 reduction reaction (CO 2 RR) because of their outstanding catalytic performance. However, precise engineering of the surface-interface electronic architecture in these catalysts to refine CO 2 adsorption and activation remains a critical hurdle. Herein, we synthesize various metastable oxyhalides, followed by in situ electrochemical reconstruction to form Bi 2 O 2 CO 3 /Bi 2 O 3 heterostructures with carbonate–bismuth–oxygen (CO 3 –Bi–O) heterosites. In situ and ex situ measurements and theoretical studies reveal that in these CO 3 –Bi–O heterosites electron accumulation in Bi zones and depletion in O regions create a localized interfacial dipole effect, promoting favorable CO 2 adsorption and activation. The resulting heterosites enhance CO 2 RR selectivity to formate (92.5%), with a 12.5% improvement at −1.2 V (vs RHE) over pure Bi 2 O 3 . The superiority of BiOBr-derived R Br -Bi 2 O 2 CO 3 /Bi 2 O 3 is demonstrated in a proof-of-concept Zn-CO 2 battery, yielding twice the power density of Bi 2 O 3 -derived l -Bi 2 O 2 CO 3 /Bi 2 O 3 . This work paves the way for electrochemical reconstruction strategies in novel CO 2 -based battery exploration.