Electrospun single iron atoms dispersed carbon nanofibers as high performance electrocatalysts toward oxygen reduction reaction in acid and alkaline media.

The metal (Fe/Co), nitrogen co-doped carbon represent an important class of oxygen reduction reaction (ORR), which can be obtained via the thermal treatment of transition-metal macrocycles (TMMs). However, the N4-chelate complex with metal atom (M-N4) moieties as major activity site for ORR are easily destroyed to form inorganic metal species during simple pyrolysis of TMMs. In this report, polyacrylonitrile (PAN) nanofibers were prepared by electrospinning containing a small amount of hemin (chloroprotoporphyrin IX iron(III), TMMs). The electrospun nanofibers were converted into Fe, N co-doped carbon nanofibers (Fe-N-CNFs) through preoxidized and thermal treatment. The PAN macromolecules can prevent hemin from aggregation during the process of pyrolysis. The Fe elemental mapping demonstrated that Fe species probably existed in a single atom state. The Fe K-edge X-ray absorption fine structure spectrum of Fe-N-CNFs proved that the Fe-N4 moieties have been successfully reserved. The X-ray photoelectron spectra of Fe-N-CNFs indicated that the amount of Fe-N4 moieties increased with the increased percent of hemin. Therefore, the Fe-N-CNFs exhibited the higher catalytic activity for ORR compared with Pt electrocatalysts. Furthermore, the Fe1-N-CNFs displayed higher stability and methanol tolerance than Pt/C.