The effect of different nitrogen sources on the electrocatalytic properties of nitrogen-doped electrospun carbon nanofibers for the oxygen reduction reaction

Nitrogen-doped carbon nanofibers (NCNFs) for use as electrocatalysts for the oxygen reduction reaction (ORR) were prepared by carbonizing electrospun polyacrylonitrile (PAN) nanofibers. In order to investigate the effect of nitrogen doping on the electrocatalytic activity different nitrogen-containing chemicals including melamine, aniline, urea, and polyaniline were added into the PAN solutions prior to electrospinning. It was found that the electrocatalytic activity of the NCNFs is strongly dependant on the type and amount of nitrogen-containing chemical added. The NCNFs which showed the best electrocatalytic activity were obtained with a aniline/PAN mass ratio of 20:3. These showed an ORR peak (vs Hg/Hg₂Cl₂) at -0.047 V in KOH electrolyte and 0.426 V in H₂SO₄ electrolyte with improved stability in both media. The present work shows that the electrocatalytic performance of the NCNFs can be improved by appropriate selection of the nitrogen doping source, resulting in a promising ORR catalyst for future application.