Porous Co(OH)2 film directly grown on nickel foam is prepared by a facile hydrothermal method.The as-prepared Co(OH)2 film possesses a structure consisting of randomly porous nanoflakes with thicknesses of 20-30 nm.The capacitive behavior of the Co(OH)2 film is investigated by cyclic voltammograms and galvanostatic charge-discharge tests in 2 mol/L KOH.The porous Co(OH)2 film exhibits a high discharge capacitance of 935 F g-1 at a current density of 2 A g-1 and excellent rate capability.The specific capacitance keeps a capacitance of 589 F g-1 when the current density increases to 40 A g-1.The specific capacitance of 82.6% is maintained after 1500 cycles at 2 A g-1.
