Insights into Nitrogen‐doped Carbon for Oxygen Reduction: The Role of Graphitic and Pyridinic Nitrogen Species

Elucidating the role of nitrogen species for oxygen reduction reaction (ORR) in nitrogen doped carbons (N/Cs) is important to explore high-performance N/C catalysts. Three N/C samples with distinct nitrogen species are synthesized. Experiments and density functional calculations show graphitic N is the key for enhancement of ORR performance.

Abstract

Nitrogen-doped carbons (N/Cs) manifest good catalytic performance for oxygen reduction reaction (ORR) for fuel cell systems. However, to date, controversies remain on the role of active sites in N/Cs. In the present study, ORR test was conducted on three N/Cs in O₂-saturated 0.1 M KOH aqueous solution, where apparent linear correlation between graphitic N contents and ORR activity was observed. Theoretical calculations demonstrated that graphitic N doping is energetically more favorable than that of pyridinic N doping for ORR and the pyridinic N leads to more preferential with 2 e ^– ORR pathway. These results reveal that graphitic N plays a key role in N/Cs mediated ORR activity. This work lays a solid foundation on identifying the active sites in heteroatom-doped carbons and can be exploited for rational design and engineering of effective carbon-based ORR catalysts.

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