Influence of Ni-Co catalyst composition on nitrogen content in carbon nanotubes

Nitrogen-containing carbon nanotubes were obtained by pyrolysis of acetonitrile (CH3CN) at 850degreesC over catalytic nanoparticles formed by the thermal decomposition of Co and Ni bimaleates or their mutual solutions. Structure and composition of synthesized samples were studied by electron microscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). It is found that the yield of the nanotubes, the quality of the layer packing, and nitrogen content in the CNx nanotubes depend on the catalyst composition. XPS of the N Is spectra show that nitrogen atoms are in two different electronic states in the carbon nanotubes. According to quantum chemical calculations these states can be ascribed to nitrogen atoms substituting for carbon atoms in the graphite network and pyridine-like atoms. It was shown that the nanotubes synthesized using catalyst with the ratio Ni/Co 1:1 contain the greatest proportion of pyridine-like nitrogen.