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

Electrochemical reduction of CO (CO RR) 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 Bi O CO nanosheets (BOC NSs) are synthesized by an in situ electrochemical anion exchange strategy from Bi O SO as a pre-catalyst. The BOC NSs achieve a high formate Faradaic efficiency (FE ) of 95.7% at -1.1 V versus reversible hydrogen electrode (vs. RHE), and maintain FE 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 BOC NSs undergo the anion exchange from Bi O SO to Bi O CO 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 CO RR.