CuO nanosheet arrays freely standing on nickel foam are prepared via a template-free growth method. The morphology of CuO nanosheet arrays is examined by scanning and transmission electron microscopy and the phase structure of nanosheets is analyzed by X-ray diffraction spectroscopy. The supercapacitance of CuO nanosheet arrays is investigated by cyclic voltammetry. galvanostatic charge/discharge test and electrochemical impedance spectroscopy. The results show that the array of CuO nanosheets forms a uniform film of around 5 mu m in thickness on nickel foam skeleton. The film is composed of clusters of arrays of nanosheets with a thickness up to around 150 nm. The CuO nanosheet arrays exhibit a specific capacitance of 569 F g(-1) at a current density of 5 mA cm(-2) in 6.0 mol dm(-3) KOH electrolyte. The capacitance loss is less than 17.5% after 500 charge/discharge cycles at 10 mA cm(-2) and with columbic efficiency higher than 93%. (C) 2011 Elsevier B.V. All rights reserved.