Preparation and electrochemical properties of nitrogen-doped multi-walled carbon nanotubes

High yield bamboo-shaped N-doped multi-walled carbon nanotubes (MWNTs), containing 2.27 at.% N, were fabricated by pyrolysis of pyridine at 800 °C in an Ar atmosphere. The electrochemical capacitive performances of this type of carbon fiber were evaluated in 6 M KOH aqueous solution. The specific capacitance of N-doped MWNT electrode is measured to be 44.3 F/g at the charge/discharge current of 1 mA, which is two times greater than that of the undoped one (19.9 F/g). The measurements also reveal that the N-doped MWNT electrode possesses lower equivalent series resistance (0.24 Ω) and higher knee frequency (1995 Hz) than the undoped one. This improvement is attributed to the unique morphology and electronic properties of N-doped MWNTs.