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

The metal oxide/nitrogen-doped carbon (NC) compounds zirconium oxide/NC (ZrO2/NC) and cerium oxide/NC (CeO2/NC) were synthesized via the pyrolysis of polyaniline on the metal oxide surface. The characterization of the ZrO2/NC and CeO2/NC catalysts showed more active CO2 reduction reaction activity than that of NC catalyst without metal oxide. Gas chromatography analysis revealed that CO and H2 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 ZrO2/NC reached 90% at − 0.73 V (vs. RHE), with the current density of CO at 5.5 mA/cm2; this Faraday efficiency value was higher than that of NC (41%), with the current density of CO at 3.1 mA/cm2. 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 CO2•− and thus promoting the CO2 reduction reaction.