Structure and electrical transport properties of carbon nanofibres/carbon nanotubes 3D hierarchical nanocomposites: Impact of the concentration of acetylacetonate catalyst

Abstract

The aim of this study was an extensive analysis of the correlations linking the structure with the electrical properties of hierarchical nanocomposites – electrospun carbon nanofibres/carbon nanotubes (eCNF/CNT). Herein, we focus primarily on the determination and separation of the impact of iron (III) acetylacetonate (Fe(Acac)3) on the structure of core-eCNFs from the overall effect it exerts on the global ordering and electrical properties of nanocomposites. The structure of materials was evaluated using highly local microscopic and diffraction techniques as well as global spectroscopic methods. The charge transport properties were determined through analysis of the temperature-dependent conductivity via Mott's variable-range hopping model. The investigation revealed that increasing concentration of Fe(Acac)3 results in higher surface density of CNTs, which affects the electrical transport in nanocomposites positively (158% increase in σ298K; notable decline in T0). However, it was proved that high catalyst concentrations simultaneously cause amorphisation of core-eCNFs and increase the activation energy of hopping conduction in them. As a consequence of the above, we estimated the concentration of Fe(Acac)3 (~3.0%), ensuring the best electrical properties. Additionally, it was demonstrated that desorption of electrically active guest molecules causes notable changes in the electronic transport in nanocomposites.