Efficient CO2 electroreduction to formate using Bi–Pb bimetallic catalysts with 2D vertical nanosheets

Abstract

CO₂ electroreduction to formate with high faradaic efficiency (FE_formate) and current density (j_formate) in a wide potential window remains a field of intense interest. Herein, Bi–Pb 2D vertically aligned nanosheets were prepared for CO₂ electroreduction to enhance the electroreduction activity and broaden the electroreduction window. The Bi–Pb nanosheet catalysts exhibited 97.8% FE_formate at −0.8 V (vs. RHE) and the highest j_formate of 53.1 mA cm⁻² at −1.1 V (vs. RHE) in a CO₂-saturated 0.5 M KHCO₃ solution, maintaining selectivity and stability over 10 h in a H-type cell. In addition, ionic liquid electrolytes further reduced the reaction activation energy (6.39 kJ mol⁻¹) of Bi–Pb nanosheet catalysts compared with 0.5 M KHCO₃ aqueous electrolytes (10.93 kJ mol⁻¹). Therefore, Bi–Pb nanosheet catalysts exhibited 92.0% FE_formate with 60.0 mA cm⁻²j_formate at −2.4 V (vs. Ag/Ag⁺), and the electroreduction window (−1.9 to −2.4 V) for FE_formate over 90% was significantly widened. Density functional theory calculations indicated that the presence of electron transfer in the Bi–Pb bimetallic catalyst reduces the Gibbs free energy of *OCHO intermediates, which is conducive to the formation of formate product. This work provides a feasible method for promoting CO₂ electroreduction to formate by preparing high-performance bimetallic catalysts.