Influence of methylimidazole isomers on ferrocene-catalysed nitrogen doped carbon nanotube synthesis

Nitrogen doped multi-walled carbon nanotubes (N-CNTs) were synthesized by the solid state pyrolysis of ferrocenylmethylimidazole or a mixture of ferrocene (FcH)/i-methylimidazole (i = 1, 2 and 4) at 800 °C at different ratios in sealed quartz tubes. Transmission electron microscopy (TEM) images confirmed that the carbon nanotubes (CNTs) obtained were doped with nitrogen to give nitrogen doped multi-walled CNTs (N-CNTs). N-CNTs showed bamboo-like structures for the CNTs produced from both ferrocenylmethylimidazole and the mixtures of FcH/i-methylimidazole at varying ratios. The study revealed that the different imidazoles produced different types/size distributions of shaped carbon nanomaterials (SCNMs) including N-CNTs with different diameters. An investigation of the bamboo structures revealed that the three methylimidazole isomers led to tubes with different individual bamboo compartment distances and different morphologies including different N contents. This confirms that the synthesis of N-CNTs is determined by fragments (ratios, types) produced by decomposition of reactants at high temperature.