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 H-2. 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.