Effect of nitrogen-containing groups on enhanced capacitive behaviors of multi-walled carbon nanotubes

In this work, electrochemical properties of surface treated multi-walled carbon nanotubes (MWNTs) are studied in supercapacitors. Nitrogen and oxygen functional groups containing MWNTs are prepared by urea and acidic treatments, respectively. The surface properties of the MWNTs are confirmed by X-ray photoelectron spectroscopy (XPS) and zeta-potential measurements. The textural properties are characterized by N2 adsorption/desorption isotherm at 77 K using the BET eqaution, BJH method, and HK method. The electrochemical properties of the MWNTs are accumulated by cyclic voltammetry, impedance spectra, and charge–discharge cycling performance in 1 M H2SO4 at room temperature. As a result, the functionalized MWNTs lead to an increase in capacitance as compared with pristine MWNTs. It suggests that the pyridinic and pyridinic-N-oxides nitrogen species have effects on the specific capacitance due to the positive charge, and thus an improved electron transfer at high current loads results, the most important functional groups affecting capacitive behaviors.

Graphical AbstractThe N1s spectra of nitrogen functionalized multi-walled carbon nanotubes are measured by X-ray photoelectron spectroscopy.Figure optionsDownload as PowerPoint slideHighlights
► Facile method of increasing elemental composition of nitrogen functional groups on carbon materials.
► Increased specific capacitance multi-walled carbon nanotubes (MWNTs) for electrode materials as high as general chemical activation process.
► Enhanced capacitive behaviors via introducing pyridinic and pyridinic-N-oxides nitrogen species onto the MWNTs.
► Improvement of electron transfer at high current loads.