Activating a novel (Bi2O3/Bi) tandem catalyst for ec CO2 conversion: an operando XRD/tomography approach

A novel Bi2O3 catalyst for the electrochemical reduction of CO2 into formate is produced on a carbon fiber cloth support (GDE) by a template-assisted Bi electrodeposition, followed by activation through thermal annealing. The faradaic efficiencies of formate production never fall below FE(formate) = 95% within an extraordinarily wide potential window of about 1100 mV. We hypothesize that the broad potential widow of formate production is due to the coupling of two distinct CO2RR mechanisms taking place (i) on the oxidic Bi2O3 foam (low overpotentials) and (ii) on the metallic Bi foam which forms at higher overpotentials. Operando X-ray diffraction and tomography techniques should be applied herein to probe the potential (and time) dependent transition of the Bi2O3 foam into its metallic state under CO2RR conditions.