The single crystalline Ni(OH)(2) nanosheets were synthesized by a simple chemical precipitation method using nickel chloride as precursors and ammonia as precipitating agent. The Ni(OH)(2) nanosheets were successfully converted to NiO nanosheets via calcination under appropriate conditions. Analytical methods such as X-ray diffraction (XRD) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Fourier transformed infrared (FTIR) spectra were employed to characterize the morphology and microstructure of the final products. The experimental results revealed that Ni(OH)(2) nanosheets were shape-preserved transformed to NiO nanosheets at 250 degrees C for 24 h. Ni(OH)(2) and NiO nanosheets were directly functionalized as supercapacitor electrodes for potential energy storage applications, whose charge-discharge properties, electrochemical impedance spectra, cyclic voltammetry, and cycle performance were examined. The experimental results show that the single-crystalline NiO nanosheets are a promising candidate for the supercapacitor electrode. They exhibit a high specific capacitance, prompt charge/discharge rate. (C) 2013 Elsevier Ltd. All rights reserved.