Anion Exchange Facilitates the In Situ Construction of Bi/Bi-O Interfaces for Enhanced Electrochemical CO₂-to-Formate Conversion Over a Wide Potential Window

Electrochemical reduction of CO2 (CO2RR) into value-added products is a promising strategy to reduce energy consumption and solve environmental issues. Formic acid/formate is one of the high-value, easy-to-collect, and economically viable products. Herein, the reconstructed Bi2O2CO3 nanosheets (BOCR NSs) are synthesized by an in situ electrochemical anion exchange strategy from Bi2O2SO4 as a pre-catalyst. The BOCR NSs achieve a high formate Faradaic efficiency (FEformate) of 95.7% at -1.1 V versus reversible hydrogen electrode (vs. RHE), and maintain FEformate above 90% in a wide potential range from -0.8 to -1.5 V in H-cell. The in situ spectroscopic studies reveal that the obtained BOCR NSs undergo the anion exchange from Bi2O2SO4 to Bi2O2CO3 and further promote the self-reduction to metallic Bi to construct Bi/Bi-O active site to facilitate the formation of OCHO* intermediate. This result demonstrates anion exchange strategy can be used to rational design high performance of the catalysts toward CO2RR.