Selective Electrochemical CO2 Reduction to Formate over Bismuth Nanosheets Derived By in-Situ Morphology Transformation of Bismuth Oxides

The electrochemical CO2 reduction reaction (CO2RR) has attracted enormous attention as a promising technology not only to mitigate CO2 accumulation, but also to convert CO2 into valuable chemicals and fuels.Formate/formic acid is a value-added product from CO2RR that is an important intermediate for chemical industries such as medicines, rubbers, leather and deicing materials. Moreover, it can be used as a source for hydrogen storage, transportation, as well as a fuel for direct formic acid fuel cells. Bismuth nanosheets (BiNSs) have been recognized as a promising catalyst for electrochemical CO2 reduction (CO2RR) to formate, but its preparation typically involves an elaborate synthesis of Bi-precursors under elevated temperature and pressure. Here, we have demonstrated a simple, low-cost preparation method for BiNSs by in-situ morphology transformation of Bi2O3 particles by simple electrochemical processing. SEM analysis showed that such transformation is exceedingly facile on the precipitated Bi2O3 particles compared to BiNPs and Oxi-BiNPs, revealing the crucial roles of oxygen and the initial morphology of Bi precursor in the exfoliation of BiNSs. The OD-BiNS exhibited superior CO2RR performance compared to the BiNPs and Oxi-BiNPs. 93% of FE was achieved with the current density of 62 mA cm−2 at −0.95 VRHE in the H-type cell. The enhanced CO2RR performance of OD-BiNSs can be attributed to its higher intrinsic activity and increased ECSA. 94% of FE with a high current density of 200 mA cm−2 was achieved in the flow cell, suggesting OD-BiNSs as a promising catalyst for practical applications of CO2RR. Our recent research on flow electrolytic cells for CO2 reduction will also be presented.