High dispersion and oxygen reduction reaction activity of Co(3)O(4) 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 Co(3)O(4)/carbon electrocatalysts. For comparison, Co(3)O(4) 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 Co(3)O(4) nanoparticles compared to the MWCNTs. In addition, many individual Co(3)O(4) 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 Co(3)O(4) nanoparticles rather than the basal planes of carbon that predominated the surface of the MWCNTs. The oxygen reduction reaction (ORR) activity of the Co(3)O(4)/pCNF composite in 0.1 mol dm(−3) KOH solution was better than that of Co(3)O(4)/MWCNTs. The N-pCNF further enhanced the ORR activity of the Co(3)O(4)/pCNFs even though the dispersion and supported amount of Co(3)O(4) nanoparticles were negligibly affected by the presence of the nitrogen species. Synergistic interactions of the Co(3)O(4) nanoparticles with N-doped CNFs contributed to the increased ORR activity.