Carbon Nanotubes Modified with Fluorine

Abstract

One of the most remarkable properties of carbon is the ability of its atoms to combine with other elements allowing a great diversity of nanostructures, e.g., carbon nanotubes (CNTs). The unique properties of these materials, such as good electrical conductivity, chemical stability, light weight, and ease of handling make them suitable materials for electrochemical applications. Recently, the insertion of heteroatoms in the carbon structure have been used in order to modify and enhance the CNTs physical and chemical properties. The present study shows the synthesis and characterization of carbon nanotubes modified with fluorine (CNTs/F). The materials were synthesized by a modified chemical vapor deposition using toluene as carbon source and ferrocene as metal catalyst for the nanotubes growth. Fluorobenzene was used as a precursor of fluorine. During the process, parameters such as synthesis temperature (900°C - 1000°C) and fluorobenzene concentration in the toluene solution (20 - 80 g/L) were varied. The effects of these factors were investigated using high-resolution scanning electron microscopy and x-ray microanalysis by energy dispersive spectroscopy (SEM-EDS), transmission electron microscopy (TEM), x-ray diffraction (XRD), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS). The results showed that the morphological and physical properties of CNTs/F, such as wall thickness and defects changed in comparison to those of pristine CNTs. According to the Raman spectroscopy results, the composite materials showed major defects in the structure. These changes can be explained by the integration of the fluorine atoms in the structure of the nanotubes, which increase the disorder of the graphitic network. Morphology, elemental composition and chemical state of the carbon-fluorine bonds will be discussed as well as their effects in the electrochemical applications in lithium-ion batteries.