Metal Oxide/Nitrogen-Doped Carbon Catalysts Enables Highly Efficient CO2 Electroreduction

The metal oxide/nitrogen-doped carbon (NC) compounds zirconium oxide/NC (ZrO 2 /NC) and cerium oxide/NC (CeO 2 /NC) were synthesized via the pyrolysis of polyaniline on the metal oxide surface. The characterization of the ZrO 2 /NC and CeO 2 /NC catalysts showed more active CO 2 reduction reaction activity than that of NC catalyst without metal oxide. Gas chromatography analysis revealed that CO and H 2 were the primary products, and no liquid-phase products were detected via proton nuclear magnetic resonance spectroscopy or high-performance liquid chromatography. The maximum Faraday efficiency of ZrO 2 /NC reached 90% at − 0.73 V (vs. RHE), with the current density of CO at 5.5 mA/cm 2 ; this Faraday efficiency value was higher than that of NC (41%), with the current density of CO at 3.1 mA/cm 2 . The interaction between the metal oxide and carbon allowed the efficient formation of defect sites, especially imine-type nitrogen, strengthening the adsorption of the key reaction intermediate CO 2 •− and thus promoting the CO 2 reduction reaction.