Achieving high current density for electrocatalytic reduction of CO2 to formate on bismuth-based catalysts

Electrocatalytic reduction of CO2 to formate is an attractive avenue for CO2 utilization. Unfortunately, existing catalysts suffer from low faradic efficiency of formate production at high current density. Here, we report a general strategy for preparing the Bi2O2CO3 nanosheet (BOC-NS) with abundant oxygen vacancies through in situ electrically driven conversion of the BiPO4 precursor. The converted BOC-NS displays high faradic efficiency of formate (FEHCOO−) (∼100%) over a wide potential region in an H-type cell and achieves a formate partial current density of −930 mA cm−2 with a FEHCOO− of 93% at −1.55 VRHE in a flow cell. Experimental results and density functional theory (DFT) calculations confirm that the BOC-NS surface with abundant oxygen vacancies benefit formate production, which stems from fast reaction kinetics toward the formation of ∗OCHO intermediate on defective Bi2O2CO3 nanosheets. This work provides helpful guidance for designing efficient electrocatalysts via in situ electrochemical transformation.