For supercapacitors, pores in electrode materials can accelerate chemical reaction kinetics by shortening ion diffusion distances and by enlarging electrolyte/electrode interfaces. This article describes a simple one-step route for the preparation of pure-phase porous Ni-3(NO3)(2)(OH)(4) nano-sheets by directly heating a mild Ni(NO3)(2) and urea solution. During heating, urea decomposed into NH3 center dot H2O, which provided a suitable alkaline environment for the formation of Ni-3(NO3)(2)(OH)(4) nano-sheets. Meanwhile, the side product, NH4NO3, created numerous pores as a pore-forming agent. After NH4NO3 removal, the specific surface areas and pore volumes of products were boosted by similar to 180-times (from 0.61 to 113.12 m(2)/g) and similar to 90-times (from 3.40 x 10(-3) to 3.17 x 10(-1)m(2)/g), respectively. As a cathode material of supercapacitor, the porous Ni-3(NO3)(2)(OH)(4) nano-sheets exhibited a high specific capacitance of 1094 F/g at an ultrahigh mass loading of 17.55 mg/cm(2), leading to an impressive areal capacitance of 19.2 F/cm(2). Furthermore, a Ni-3(NO3)(2)(OH)(4) nano-sheet//commercial active carbon asymmetric supercapacitor was constructed and delivered an energy density of 33.2 Wh/Kg at a power density of 190.5 W/Kg, based on the mass of active materials on both electrodes. (C) 2017 Published by Elsevier B.V.