Boron-Doped Oxidized Carbon Black Hybridizing Bismuth Oxide for Electrocatalytic CO₂ to Formate at a Large Current Density

The electrochemical CO2 reduction reaction (CO2RR) is a feasible green route for chemical production, but the design of an efficient catalyst is still challenging to fulfill the requirement of an industrial current. In this study, we reported a hybrid material Bi@BOC composed of boron-doped oxidized carbon black and bismuth oxide for the conversion of the CO2 to formate under a large current density. Bi@BOC underwent an irreversible in situ reconstruction during the CO2RR process to form a Bi2O3/Bi2O2CO3 composite as the active sites that facilitated the production of formate across a broad current range of 300–800 mA cm–2, e.g. achieving a Faradaic efficiency of formate (FEformate) > 95% at 800 mA cm–2. Additionally, Bi@BOC maintained the FEformate above 80% at 100 mA cm–2 for 12 h in a membrane electrode assembly (MEA) reactor. Operando X-ray absorption fine structure (XAFS) spectra and in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) confirmed the structural reconstruction into Bi2O2CO3 and unraveled the roles of hybridizing B-doped carbon with bismuth: 1) promotion of the abundant Bi2O2CO3 formation with high stability for the reversible valence variation of the Bi species; 2) improvement of the conductivity to accelerate the charge transfer; and 3) provision of the better hydrophobicity to inhibit the hydrogen evolution side reaction.