Electrochemical Reduction of CO2 on Nitrogen-Doped Carbon Catalysts With and Without Iron

The carbon dioxide reduction reaction (CO2RR) catalyzed by N-doped carbon materials was studied under operando conditions by on line differential electrochemical mass spectrometry and in-line gas chromatography. Fe/NC electrocatalysts were synthesized by using a Fe+2-impregnated pyridyl/triazine complex heat treated at 800 degrees C in nitrogen (Fe/NC(N-2)) or ammonia (Fe/NC(NH3)) atmospheres; an iron-free nitrogen-doped carbon electrocatalyst (NC(NH3)) was also synthesized and included for comparison. Here, superior CO faradaic efficiencies were evidenced for NC(NH3) compared to Fe/NC(NH3), independently of the applied electrode potential; however, much larger overall catalytic activity for the promotion of the CO2RR and/or HER has been observed for Fe/NC(NH3), generating different stoichiometric ratios of syngas (CO/H-2). Another important evidence is that N-pyridinic groups, even in absence of Fe-N-4 moieties and presence of high iron nanoparticles loading, play an important role as active sites for selective CO2 reduction to CO at low overpotentials.