Structural analysis and oxygen reduction reaction activity in bamboo-like nitrogen-doped carbon nanotubes containing localized nitrogen in nodal regions

Abstract Nitrogen-doped carbon nanotubes (N-CNTs) act as a metal-free catalyst for oxygen reduction reaction (ORR), but improving the ORR activity of N-CNTs remains challenging due to a lack of structural information. The N-CNTs with higher nitrogen concentration (an average surface nitrogen concentrations, 14.3 at.%) than the N-CNTs fabricated by conventional chemical vapor deposition method were synthesized using a dielectric barrier discharge in high pressure nitrogen and the spatial distribution of nitrogen in the N-CNTs was demonstrated by transmission electron microscopy in conjunction with electron energy loss spectroscopy. Nitrogen atoms were found to be concentrated at nodal regions in the bamboo-like structure, at concentrations above 23 at.%. At the point of the ORR, the highest onset potential was observed in the N-CNTs due to relatively highly incorporated pyridine-like nitrogen.