Preparation of high purity helical carbon nanofibers by the catalytic decomposition of acetylene and their growth mechanism Original Research Article

Helical nanofibers were synthesized at 271 °C using acetylene gas as the reactant and copper nanocrystals, produced by decomposition of copper tartrate, as the catalyst. Their chemical structure was confirmed to be organic compounds containing Cdouble bond; length as m-dashC groups using characterization by FT-IR, 1H NMR and elemental analyses. The morphologies of the catalyst before, during and after the fiber growth were observed by SEM and TEM, and the results reveal that the shape of the copper nanoparticles changes from quasi-spherical to polyhedral during the adsorption of acetylene. Chemisorption of acetylene on different planes of the copper crystal was simulated by density functional theory calculations under the generalized gradient approximation. The adsorption energy on the (1 1 1), (1 0 0) and (1 1 0) planes of Cu was investigated to address the interaction modes between acetylene and Cu surfaces. The adsorbability is in the order (1 0 0) > (1 1 1) > (1 1 0). Based on the experimental and theoretical evidence, a growth mechanism of coordination polymerization and asymmetric growth on distinctive crystal planes was proposed to interpret the structural and morphological variations of the nanofibers.