Bi₂O₂CO₃ Nanosheets as Electrocatalysts for Selective Reduction of CO₂ to Formate at Low Overpotential

Electrochemical reduction of carbon dioxide (CO₂) to formate is energetically inefficient because a high overpotential (>1.0 V) is required for most traditional catalysts. In this work, Bi₂O₂CO₃ (BOC) nanosheets were synthesized as electrocatalysts of CO₂ reduction for the first time. Additionally, BOC decorated on the glassy carbon electrode was reduced in situ to metal Bi (RB) for comparing the catalytic performance toward CO₂ reduction to that of BOC. The maximum faradaic efficiency of BOC was 83% at an overpotential of 0.59 V, which is a little lower than that of RB (90% obtained at the overpotential of 0.99 V). However, the overpotential for the reduction of CO₂ to formate on BOC is obviously decreased compared to that on RB. After 27 h of electrolysis, approximately 80% formate selectivity was obtained using the BOC catalyst. According to the experimental results and the related literature, a new mechanism for the CO₂ reduction reaction on BOC was proposed, which may play a guiding role in future catalyst design.