Facile and scalable functionalization of carbon nanofibers for oxygen reduction reaction: Role of nitrogen precursor and non-ionic dispersant

[Display omitted] •CNFis functionalized with PDDA using a simple ultrasonication methodology.•Triton X-100 masks some of the reactive edge plane sites along with unbundling CNF.•PDDA-CNF electrode shows an efficient four-electron ORR pathway.•Onset potential and limiting current density of PDDA-CNF are comparable to Pt/C.•The higher ORR activity is due to the presence of reactive edge plane sites. The surface modification of carbon nanomaterials with heteroatoms improves their electrocatalytic activity for oxygen reduction reaction (ORR). The present work reports the surface modification of carbon nanofiber (CNF) with poly(diallyldimethylammonium) chloride (PDDA) and Triton X-100. PDDA behaves as an electron-acceptor, and the intermolecular charge transfer from CNF to PDDA creates delocalized positive charge sites at the edge and basal plane sites of CNF. Triton X-100 disperses CNF, but also acts as a masking agent to obstruct the intermolecular charge transfer between CNF and PDDA. The surface modification of CNF with (PDDA+Triton X-100) is characterized in terms of FESEM, TEM, EDX, Raman, FTIR and TGA. The electrocatalytic activity of the conjugated systems (CNF+PDDA and CNF+Triton X-100+PDDA) is investigated in terms of cyclic voltammetry and linear sweep voltammetry. The reduction of oxygen at PDDA-CNF occurs via a more efficient four-electron (n=3.9) pathway in 0.1M KOH and exhibits a limiting diffusion current density of 3.23mAcm−2, which is closer to the Pt/C electrode (3.41mAcm−2). PDDA-CNF even outperforms PDDA-CNT or graphene for the ORR performance owing to their special morphological features. This study thus provides a facile and viable strategy for the scalable production of CNF based ORR electrocatalysts.