Behavior of NiO-MnO2/MWCNT composites for use in a supercapacitor

NiO-MnO2/MWCNT composite was formed by a simple chemical precipitation method using a chelating agent and Ni and Mn hydroxides on MWCNT. The NiO-MnO2/MWCNT was pretreated by ultrasonication, followed by thermal annealing at 300 degrees C. The material obtained was applied as an electrode in a supercapacitor. FT-IR, EDS, XRD, FE-SEM and FE-TEM were used to characterize the structural features. The results show that a nanosized NiO-MnO2 layer covered the surface of the MWCNT, and the original structure of the MWCNT was retained during the coating process. The capacitive behavior of the NiO-MnO2/MWCNT electrode was investigated by cyclic voltammetry and galvanostatic charge/discharge methods in a 6 M KOH aqueous solution. The cyclic voltammetry curves demonstrated that the maximum specific capacitance of the NiO-MnO2/MWCNT electrode was 193.50 Fg(-1), which is significantly higher than that of an MWCNT electrode. The results show that both the MWCNT and NiO-MnO2/MWCNT electrodes exhibited capacitive behaviors, and the NiO-MnO2 layer increased the capacitance of the supercapacitor. (C) 2011 Elsevier B.V. All rights reserved.