A hierarchically porous NiO film on nickel foam substrate is prepared by a facile ammonia-evaporation method. The self-assembled film possesses a structure consisting of NiO triangular prisms and randomly porous NiO nanoflakes. The pseudocapacitive behaviors of the porous NiO film are investigated by cyclic voltammograms and galvanostatic charge-discharge tests in 1 M KOH. The hierarchically porous NiO film exhibits a high discharge capacitance and excellent rate capability with 232 F g(-1), 229 F g(-1), 213 F g(-1) and 200 F g(-1) at 2, 4, 10, and 20 A g(-1), respectively. The specific capacitance of 87% is maintained from 2 A g(-1) to 20 A g(-1). The porous NiO film also shows rather good cycling stability and exhibits a specific capacitance of 348 F g(-1) after 4000 cycles. (C) 2011 Elsevier B.V. All rights reserved.