Gas phase electrochemical conversion of humidified CO2 to CO and H2 on proton-exchange and alkaline anion-exchange membrane fuel cell reactors

Fuel cell reactors or electrolyzers based on alkaline anion-exchange membrane and proton exchange membrane (AAEM & PEM) are investigated for gas phase electrochemical conversion of humidified CO2 under identical conditions, using conventional Pt/C, Pd/C and Cu/CNTs as cathodic catalysts. Humidified CO2 can be converted to H2 and CO via the AAEM based fuel cell reactors with an estimated onset potential of −1.0 V using Cu/CNT as cathodic catalyst, while PEM based fuel cell reactors can only produce H2 under identical conditions. This can be attributed to the suppressed hydrogen evolution and enhanced CO2 reduction in the case of AAEM based reactor. Remarkably, AAEM based reactor with Cu/CNT cathode catalysts shows a higher activity (8.88 μmol h−1 cm−2) to convert CO2 to CO than that of Pd/C (7.59 μmol h−1 cm−2) and Pt/C (0.75 μmol h−1 cm−2) at the same catalyst loading. This study indicates that AAEM based reactor is able to realize the gas phase electrochemical conversion of CO2, providing a viable strategy for CO2 utilization and conversion to useful fuels.