Synthesis and Electrochemical Performance of Nitrogen-Doped Carbon Nanotubes

We treated carbon nanotubes (CNTs) with hydrazine hydrate and diethylenetriamine separately and characterized them using scanning electron spectroscopy (SEM) and X-ray photoelectron spectroscopy (XPS). SEM indicated that the treated CNTs retained the length/diameter ratio of the pure CNTs and XPS showed that nitrogen was doped in the CNTs. XPS analysis also indicated that the carbon/nitrogen atomic ratio of the CNTs treated by hydrazine hydrate was 95/2, which was much higher than the 96/0.5 for the CNTs treated by diethylenetriamine. The hydrophilicity of the CNTs was found to be much higher after N-doping and it increased with an increase in the N content. Therefore, the water dispersibility of the N-doped CNTs treated by hydrazine hydrate was better than that of the N-doped CNTs treated by diethylenetriamine. As electrode materials for electrochemical capacitors, nitrogen functional groups contribute to the pseudo-Faradic capacitance but their cyclic performance still needs to be improved. Because of the good hydrophilicity of the N-doping CNTs, which improves the wettability of the CNTs for the electrolyte, the specific capacitance of the N-doping CNT electrode is still slightly higher than that of the pure CNT electrode after cycling.