Nanocrystalline NiO was synthesized by high temperature solid-state (HTSS) method and microwave (MW) method. The structure of the samples was examined by X-ray. Electro-chemical properties were examined by galvanostatic charge-discharge measurements, cyclic voltammetry and electrical impedance spectroscopy. The results showed that the particle sizes of the NiO prepared by MW and HTSS were 34.6 and 75.5 nm. The specific capacitance of MW and HTSS were 186 and 97 F g(-1), which decreased to 170 and 74 F g(-1) after 1000 cycles. It revealed that the NiO materials prepared by MW exhibited good specific capacitance and cycling performance, which had the high surface redox reactivity due to its special nanostructures. (c) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.