Preparation of Co3O4 nanowires grown on nickel foam with superior electrochemical capacitance

Co3O4 nanowires have been successfully synthesized on nickel foam by a hydrothermal method. The morphology of Co3O4 is examined by scanning and transmission electron microscopy and the phase structure of Co3O4 nanowires is confirmed by X-ray diffraction. The electrochemical capacitance behavior of the Co3O4 nanowires electrode is investigated by cyclic voltammetry, galvanostatic charge/discharge test and electrochemical impedance spectroscopy in 6 mol dm(-3) KOH solution. The results show that the Co3O4 nanowires have diameters of around 100 nm and the lengths up to 1-2 mu m. The specific capacitance of Co3O4 nanowires is 1019.58 F g(-1) at 3.38 A g(-1) and 466.06 F g(-1) at 33.80 A g(-1). The capacitance loss is less than 5% after 1000 charge/discharge cycles at 3.38 A g(-1) and with columbic efficiency higher than 98%. The enhancement of pseudocapacitive properties at a higher charging/discharging rate is due to the porous nanostructure and the high utilization of active material. (C) 2012 Elsevier Ltd. All rights reserved.