Oxidation and reduction of multiwalled carbon nanotubes — preparation and characterization

This work presents the use of a modified titration (Boehm's) process which is a simple and efficient method to quantify functional groups formed on the surface of oxidized multiwalled carbon nanotubes (MWCNTs). The MWCNTs were synthesized via chemical vapor deposition (CVD) and were purified through a hydrochloric acid treatment. Purified material was oxidized in a mixture of nitric and sulfuric acids. A part of oxidized sample was reduced with sodium borohydrate (NaBH4). Boehm's titration is a complimentary method to Fourier Transform Infrared spectroscopy (FT-IR) with which to investigate the changes to the surface of oxidized MWCNTs after the reduction process. The reduction process led to threefold increase in the hydroxyl group content. In addition, the pristine, oxidized and reduced samples were investigated by thermogravimetry analysis (TGA) and Raman spectroscopy.