Partic. vol. 9 no. 5 pp. 465-470 (October 2011)
doi: 10.1016/j.partic.2011.02.009

Effects of bimetallic catalysts on synthesis of nitrogen-doped carbon nanotubes as nanoscale energetic materials

Hao Liu^a, Yong Zhang^a, Ruying Li^a, Xueliang Sun^a,*, Hakima Abou-Rachid^b,*

xsun@eng.uwo.cahakima.abou-rachid@drdc-rddc.gc.ca

Abstract

Well aligned nitrogen-doped carbon nanotubes (CN_x-NTs), as energetic materials, are synthesized on a silicon substrate by aerosol-assisted chemical vapor deposition. Tungsten (W) and molybdenum (Mo) metals are respectively introduced to combine with iron (Fe) to act as a bimetallic co-catalyst layer. Correlations between the composition and shape of the co-catalyst and morphology, size, growth rate and nitrogen doping amount of the synthesized CN_x-NTs are investigated by secondary and backscattered electron imaging in a field emission scanning electron microscope (FESEM) and X-ray photoelectron spectrometer (XPS). Compared to pure iron catalyst, W–Fe co-catalyst can result in lower growth rate, larger diameter and wider size distribution of the CN_x-NTs; while incorporation of molybdenum into the iron catalyst layer can reduce the diameter and size distribution of the nanotubes. Compared to the sole iron catalyst, Fe–W catalyst impedes nitrogen doping while Fe–Mo catalyst promotes the incorporation of nitrogen into the nanotubes. The present work indicates that CN_x-NTs with modulated size, growth rate and nitrogen doping concentration are expected to be synthesized by tuning the size and composition of co-catalysts, which may find great potential in producing CNx-NTs with controlled structure and properties.

Graphical abstract

Keywords

Nitrogen doped carbon nanotubes; Chemical vapor deposition; Bimetallic catalyst