Comparative investigation of CO2 and oxygen reduction on Fe/N/C catalysts

Fe/N/C catalysts have been investigated as promising non-noble metal catalysts for both CO2 reduction reaction (CO2RR) and oxygen reduction reaction (ORR). However, it is unclear whether both reactions hold the same active sites. In this study, the Fe/N/C catalysts were subjected to oxidation treatment in O2 at different temperatures to tune the reactivity. It was found that the oxidation treatment exhibits inverse effects on the CO2RR and ORR. The CO2RR activity was enhanced while ORR activity was suppressed after the oxidation treatment at temperatures from 80 to 240 °C. This result indicates that CO2RR and ORR occur at different active sites. Furthermore, it was evidenced that pyrrolic N increases significantly upon the oxidation treatment, similar to the variation tendency of the CO2RR activity, which suggests that pyrrolic N is highly relevant to the CO2RR on Fe/N/C catalysts.