Preparation and supercapacitor performance of nitrogen-doped carbon nanotubes from polyaniline modification

Abstract

Nitrogen-doped carbon nanotubes (NCNTs) were prepared by carbonization of polyanilinecoated CNTs that were synthesized by in situ polymerization of aniline on the CNT surface. The laser Raman spectroscopy, transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS) indicated that carbonization treatment of the polyaniline (PANI) coated CNTs produced NCNTs owning the core-shell structure of a nitrogen-doped carbon shell and a CNT core, without destroying the intrinsic CNT structure. By increasing the aniline amount, the N-doped layer of the NCNTs became thicker, and the amount of nitrogen doping increased from 7.06% to 8.64% (mass fraction). As the supercapacitor electrode material, the NCNTs capacitance in 6 mol·L-1 aqueous KOH solution increased from 107 to 205 F·g-1 as the N-doped layer thickness decreased, which was much higher than the capacitance of 10 F·g-1 for the pristine CNTs. Especially, NCNT electrodes displayed good cyclability, maintaining 92.8%-97.1% of the initial capacitance after 1000 charge-discharge cycles. The high capacitance and good cyclability of the NCNTs as a supercapacitor electrode material can be attributed to the pseudo-Faradic capacitance and improved hydrophility contributed by the nitrogen functional groups and the core-shell structure of the NCNTs, respectively.