Nitrogen doped carbon nanotubes decorated with iron carbide nanoparticles and their electrochemical capacitance

Abstract

Different ethanol-benzylamine (EB) ratio (9/1 v/v and 1/1 v/v) reaction mixtures were prepared for the synthesis of nitrogen doped multiwalled carbon nanotubes (N-MWCNTs). The morphology of the synthesized sample depends of the used catalyst percentage, 1 wt% or 3 wt%, during the synthesis. In low ferrocene concentration, EB91-1 wt % and EB11-1 wt% samples are mainly composed by N-MWCNTs with iron-carbide nanoparticles at their tips, whereas at high ferrocene concentration, EB91-3 wt % and EB11-3 wt% samples are composed by a mix of N-MWCNTs and carbon nano-onions (CNOs) with iron-carbide core. The way in which CNOs are distributed in EB91-3 wt% and EB11-3 wt% samples is related to the ethanol ratio used in the reaction mixture. In EB91-3 wt% sample, CNOs are distributed more homogeneously on the surfaces of the N-MWCNTs, while EB11-3 wt% sample, CNOs are segregated from N-MWCNTs. High ethanol ratio in the reaction mixture increases the probability of attaching oxygenated groups on N-MWCNTs surfaces, i.e. the surfaces functionalization is carried out during the synthesis, making possible CNOs anchoring on N-MWCNTs walls. This difference in morphology in the sample plays an important role for the high electrochemical capacitance in the EB91-3 wt% samples compared with other samples.