The Synthesis of Nitrogen-Doped Multiwalled Carbon Nanotubes Using an Fe-Co/CaCO3 Catalyst
ACVDmethod was used to prepare high-quality nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) using acetonitrile as the nitrogen and carbon source and acetylene as a carbon source over an Fe-Co/CaCO3 catalyst in the temperature range 700–850 °C. This represents a continuation of earlier work in which Fe-Co on CaCO3 was used to make undoped carbon nanotubes. The effect of synthesis parameters (growth temperature and CH3CN vaporization temperature) on the yield, size, quality, morphology and thermal stability of the N-MWCNTs was studied. The resulting materials were characterized by TEM,
SEM, TGA, BET, XPS, CN elemental analysis and Raman spectroscopy. TEM analysis revealed that the nanotubes exhibit bamboo-like structures with rough surfaces and a relatively uniform diameter. The bamboo compartment distance decreased with increase in synthesis temperature due to the increased nitrogen content inN-MWCNTs. The SEM examination showed that at high synthesis temperatures carbon spheres (CSs) with chain-like morphology and large sizes were also formed along with the N-MWCNTs. The XPS and CN elemental analysis revealed that nitrogen atoms were successfully doped into the carbon walls. The amount of nitrogen incorporated in the N-MWCNTs varied with increasing growth time and CH3CN vaporization temperature.
Keywords: Carbon nanotubes, CVD synthesis, nitrogen doping, acetonitrile, Fe-Co/CaCO3 catalyst
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