▎ 摘　　要

This article reports a facile preparation of NiO/graphene composite by the combination of a controlled refluxing method with water based solvent in the presence of cetyltrimethylammonium bromide and subsequent annealing. X-ray diffraction and scanning electron microscopy reveal that the graphene nanosheets are uniformly wrapped by hierarchical porous NiO spheres with three-dimension hierarchical structure in the product. The composite shows highly improved electrochemical performance as electrode material for supercapacitor. The three-dimension hierarchical structure NiO/graphene composite delivers a first discharge capacitance of 555 F g(-1) and remains a reversible capacitance up to 504 F g(-1) after 2000 cycles at a current of 1 A g(-1) in three-electrode system. Contrarily, the pure NiO shows only a first discharge capacitance of 166 F g(-1) and remains only a reversible capacitance of 107 F g(-1) after 2000 cycles. The NiO/graphene composite also exhibits ameliorative rate capacitance of 402.9 F g(-1) at the current density of 5 A g(-1). The enhanced electrochemical performances are ascribed to the higher surface area, the stable three-dimension hierarchical structure and the synergistic effects between the conductive graphene and porous NiO spheres. (C) 2014 Elsevier B. V. All rights reserved.