Nitrogen-doped carbon nanotubes with enhanced capacitance for electrochemical applications

Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) were synthesized with a very low ferrocene concentration by aerosol-assisted chemical vapor deposition (AACVD). In the AACVD experiments, a solution of benzylamine and ferrocene (0.05 wt.%) was used for 30 min at two different temperatures (800 °C and 850 °C) and gas flow rates (3 L min -1 and 3.6 L min -1 ). The N-MWCNTs were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Characterizations revealed that the morphology, size, and surface chemistry were highly sensitive to the growth temperature and gas flow rate. Our main findings were as follows: (i) a high gas flow rate favored the presence of N-H groups, (ii) low growth temperatures favored nitrogen doping, and (iii) relatively high areal capacitance (307 μF cm -2 ) and (3172 μF cm -2 ) for EIS and galvanostatic charge/discharge, respectively, which was mainly due to pyrrolic nitrogen. These findings highlight the potential of N-doped MWCNTs as promising materials for energy storage devices.