Novel non-covalent sulfonated multiwalled carbon nanotubes from p-toluenesulfonic acid/glucose doped polypyrrole for electrochemical capacitors

A novel and facile non-covalent process was applied to sulfonate multiwalled carbon nanotubes (MWCNTs) with a high –SO3H loading carbonaceous (C-SO3H). Then the sulfonated multi-walled carbon nanotubes/polypyrrole nanocomposite (MWCNTs/C-SO3H/PPy) was synthesized by the in situ chemical polymerization of pyrrole on the non-covalent sulfonated MWCNTs (MWCNTs/C-SO3H) using ammonium persulfate as oxidant at low-temperature. Fourier transform infrared (FT-IR) spectra confirm the modification of MWCNTs and an existence of interaction between the –SO3H group of the modified MWCNTs and the N–H group of PPy. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), FT-IR and ultraviolet–visible (UV–vis) spectra show that uniform PPy layer coated on the sidewall of MWCNTs/C-SO3H. The electrochemical properties of the MWCNTs/C-SO3H/PPy composite were studied by cyclic voltammetry and galvanostatic charge/discharge test. The composite possesses good rate response and stable specific capacitance, the specific capacitance loss is only 3% even after the 1000 cycles.

Research highlights
► A novel non-covalent method to sulfonate multiwalled carbon nanotubes (MWCNTs) and efficiently improve the dispersibility of MWCNTs.
► The sulfonated MWCNTs used to prepare the composite with polypyrrole for electrochemical capacitors.
► The composite electrode showed superior electrochemical cyclability.