Carbon sponge-type nanostructures based on coaxial nitrogen-doped multiwalled carbon nanotubes grown by CVD using benzylamine as precursor

Carbon sponges-type nanostructures (CSTN) based on coaxial nitrogen-doped multiwalled carbon nanotubes (CA-MWCNTs) were synthesized using the aerosol assisted chemical vapor deposition method involving the decomposition of a mixture of ferrocene, benzylamine, thiophene, and ethanol at 1020 °C under a flow of H2/Ar. Sample morphology and composition profiles were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and thermogravimetric analysis (TGA). SEM and TEM characterizations demonstrated that the CA-MWCNTs consisted of a core MWCNT surrounded by graphite materials with low crystallinity which was confirmed by XRD and Raman spectroscopy. Depending where the CSTN were collected along the reactor, three types of core MWCNTs morphologies were found: (1) N-doped MWCNTs with a bamboo shape and zigzagged growth, (2) straight MWCNTs, and (3) wavy MWCNTs. The carbon CSTN showed to be highly hydrophobic with outstanding oil absorption properties. XPS characterizations suggest the presence of water-fearing chemical groups such as ester- and ethoxy-groups anchored on the surface of the CA-MWCNTs. The mechanism in which the three types of MWCNTs are formed, the nature of the shell disordered graphite materials, and the hydrophobicity of the carbon sponges-type are thoroughly discussed.

Nitrogen-doped carbon sponges were synthesized by the chemical vapor deposition method. A deconvolution analysis of graphite peak (002) of samples revealed an increase of the inter-layers distance, suggesting the presence of atoms hosted inside the layers. Results for C1s and O1s revealed interesting trends indicating the presence of ester and ethoxy functional groups likely attached to the surface of carbon fibers. The presence of these functional groups could explain the super hydrophobicity of our carbon sponge type structures.346