Based on the thermal decomposition and phase transition at elevated temperature, the Cu-4(SO4)(OH)(6) precursor synthesized by a hydrothermal method could be converted into 3D nanoporous CuO. The nanoporous CuO retained the bamboo leaf-like shape and was composed of nanocrysals with grain size of 5080 nm. The CuO electrode was very stable and exhibited a specific capacitance of 269.6 F g(-1) at a current density of 0.25 A g(-1). The CuO electrode could be cycled at least 500 cycles, and the capacitance retention ratio was as 88.79% at the current density of 2 A g(-1). (C) 2017 Elsevier B.V. All rights reserved.