Abstract

An in situ coating technique was developed to prepare a manganese dioxide/multi-walled carbon nanotube (MnO2/MWCNT) composite, which exhibits excellent energy storage capacity. An alkaline KMnO4 solution was first used to oxidize and open the ends of pristine MWCNT, and citric acid was then added as a reductant to form the composite. TEM, HR-TEM, XRD, TG–DSC, FT-IR, Raman and XPS methods were used to characterize the structural features. Cyclic voltammetry and electrochemical impedance spectroscopy measurements were used to investigate the electrochemical behavior of the samples. Results show that a nanosized ε-MnO2 uniform layer covered the surface of the MWCNT and the original structure of the pristine MWCNT was retained during the coating process. The cyclic voltammetry curves demonstrate that the specific capacitance of the composite electrode reaches 250.5 F/g, which is significantly higher than that of a pure MWCNT electrode. The favorable capacitance performance is confirmed by the impedance spectra.