High dispersion and oxygen reduction reaction activity of CoO nanoparticles on platelet-type carbon nanofibers.

In this study, platelet-type carbon nanofibers prepared by the liquid phase carbonization of polymers in the pores of a porous anodic alumina template were used to prepare the CoO/carbon electrocatalysts. For comparison, CoO nanoparticles were also deposited on multiwall carbon nanotubes (MWCNTs). Both the nitrogen-free platelet-type carbon nanofibers (pCNFs) and the nitrogen-containing analogue (N-pCNFs) exhibited better dispersion and higher amount of deposited CoO nanoparticles compared to the MWCNTs. In addition, many individual CoO nanoparticles were deposited separately on pCNF and N-pCNF, whereas aggregated deposition was commonplace on MWCNTs. The results indicated that the side wall of the pCNFs, which consisted of carbon edge planes, was the preferential nucleation site of CoO nanoparticles rather than the basal planes of carbon that predominated the surface of the MWCNTs. The oxygen reduction reaction (ORR) activity of the CoO/pCNF composite in 0.1 mol dm KOH solution was better than that of CoO/MWCNTs. The N-pCNF further enhanced the ORR activity of the CoO/pCNFs even though the dispersion and supported amount of CoO nanoparticles were negligibly affected by the presence of the nitrogen species. Synergistic interactions of the CoO nanoparticles with N-doped CNFs contributed to the increased ORR activity.