Electrocatalytic oxygen-reduction reaction on a carbon nanofiber/carbon paper composite

A carbon nanofiber/carbon paper (CNF/CP) composite was synthesized directly on CP by a catalytic chemical vapor-deposition method, and the physicochemical properties of and oxygen-reduction reaction (ORR) on this composite were investigated. Scanning electron microscopy shows that the CNFs are uniformly distributed on the CP, and high-resolution transmission electron microscopy results show that the CNFs have a narrow size distribution. The CNF/CP composite has a large surface area, and its mesoporous character is confirmed by N2 physisorption. Raman spectrum studies show that the CNF/CP composite has a high ratio of edge atoms to basal atoms compared with that of CP. From cyclic voltammetry studies, the CNF/CP composite was found to be more active than CP in terms of ORR, which may be due to the contribution from the CNFs. The CNF/CP composite shows a higher exchange current density and more positive equilibrium potential than CP, as verified by Tafel analysis. Moreover, linear-sweep voltammetry confirms that ORR on the CNF/CP composite is conducted through a two-electron reaction pathway.