Understanding Selective Reduction of CO₂ to CO on Modified Carbon Electrocatalysts

Modified carbon powders are attractive electrocatalysts for chemical conversion due to their low cost and high activity. Here, we demonstrate that electrochemical conversion activities of CO₂ to CO in aqueous media are enhanced by the incorporation of transition metals into nitrogen-doped carbon (M−N/C; M=Fe, Co, Cu). The type of the metals is thereby critical to achieve selective CO production over H₂. Among M−N/C and N/C catalysts, Fe−N/C exhibited the highest faradaic efficiency for CO conversion, significantly enhanced compared with the metal-free N-doped carbon electrocatalyst. In addition, the catalysts containing higher pyridinic N and graphitic N but lower pyrrolic N contents favor CO production at lower bias potentials. Meanwhile, the total amount of N content in the carbon material is less important. Our CO₂ reduction reaction results combined with X-ray photoelectron spectroscopy analysis propose that the modification of nitrogen states in the carbon structure is crucial in CO2RR activity.