Electrochemical and Computational Study of Oxygen Reduction Reaction on Nonprecious Transition Metal/Nitrogen Doped Carbon Nanofibers in Acid Medium

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In this study, we performed both electrochemical measurements, such as the rotating disk electrode and the rotating ring-disk electrode techniques, and density functional theory (DFT) calculations to investigate oxygen reduction reaction (ORR) on nonprecious transition metal/nitrogen doped carbon nanofiber (Fe/N/C and Co/N/C) catalysts in acid medium. The nanofiber catalysts were synthesized by electrospinning and subsequent heat treatment procedures. Our electrochemical measurements showed that the pyrolyzed Fe/N/C catalyst possesses higher activity for ORR than the pyrolyzed Co/N/C catalyst and could promote four-electron (4e−) ORR. In comparison, O2 electroreduction was found to proceed mainly with 2e− pathway on the Co/N/C catalyst. To gain insights into underlying catalytic mechanisms, we calculated the adsorption energies of all possible chemical species and the activation energies for O–O bond dissociation reactions involved in ORR on the FeN4 and CoN4 active sites embedded in graphene. Our DFT cal...