N-doped MWCNTs from catalyst-free, direct pyrolysis of commercial glue

Abstract

We report a unique, catalyst-free, direct pyrolysis process to obtain nitrogen-doped multiwall carbon nanotubes (N-MWCNTs). The process includes the polymerization of ethyl cyanoacrylate (ECA) based commercial super glue with aqueous NaCl solution. The resultant poly-ethyl cyanoacrylate (PECA)-NaCl composite was washed to remove NaCl and subsequently calcined at 1000 °C in an inert atmosphere to obtain carbon nanotubes. The field emission scanning electron microscopy and high-resolution transmission electron microscopy studies confirm that these are nitrogen-doped multiwall carbon nanotubes (N-MWCNTs) with diameters in the range of 80–110 nm. Compared to conventional MWCNTs, these nanotubes exhibit distinct multilayer stacking of carbon with short-range ordering with interlayer spacing slightly larger than graphitic carbon. XPS studies reveal the presence of doped nitrogen substituting for carbon atoms, whereas Raman spectroscopy data shows that these nitrogen-doped nanotubes exhibit nanocrystalline, graphitic carbon. Washing of PECA-NaCl composite results in the removal of NaCl leading to the unique porous PECA intermediate structure. These unique morphological changes and structural transformations of PECA in DI water along with the peculiar degradation behavior of PECA during the heat treatment process may be responsible for the formation of N-MWCNTs.