Facile preparation and electrochemical characterization of cobalt oxide/multi-walled carbon nanotube composites for supercapacitors

A series of cobalt oxide/multi-walled carbon nanotube (Co3O4/MWCNT) composites are successfully synthesized by a facile chemical co-precipitation method followed by a simple thermal treatment process. The morphology and structure of as-obtained composites are characterized by X-ray diffraction, scanning electron microscopy, and N-2-adsorption/desorption measurements, and the electrochemical properties are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). For all Co3O4/MWCNT composites, MWCNTs are well dispersed in the loosely packed Co3O4 nanoparticles. Among them, the Co3O4-5%MWCNT composite exhibits the highest specific surface area of 137 m(2) g(-1) and a mesoporous structure with a narrow distribution of pore size from 2 to 10 nm. Because of the synergistic effects coming from Co3O4 nanoparticles and MWCNTs, the electrochemical performances of pure Co3O4 material are significantly improved after adding MWCNTs. The Co3O4-5%MWCNT composite shows the largest specific capacitance of 418 F g(-1) at a current density of 0.625 A g(-1) in 2 M KOH electrolyte. Furthermore, this composite exhibits good cycling stability and life-time. Therefore, based on the above investigation, such Co3O4/MWCNT composite could be a potential candidate for supercapacitors. (C) 2011 Elsevier B.V. All rights reserved.