Design and synthesis of NiO nanoflakes/graphene nanocomposite as high performance electrodes of pseudocapacitor

In this contribution, nickel oxide (NiO) nanoflakes/graphene (NiO/G) nanocomposites have been prepared by a simple hydrothermal method followed by a thermal treatment with N-2 gas. NiO nanoflakes (similar to 30-80 nm in diameter) are uniformly anchored on graphene sheets in a layer-by-layer form, which effectively prevents the aggregation of NiO nanoflakes and offers two-dimensional (2D) diffusion channels for the transportation of electrons and ions. Compared to bare NiO nanoflakes, the NiO/G composite electrode exhibits improved electrochemical properties. The specific capacitances of the NiO/G electrode are 240 F g(-1) at 5 A g(-1) and 220 F g(-1) at 10 A g(-1), which are much higher than those of the NiO electrode (i.e., 100 F g(-1) at 5 A g(-1) and 90 F g(-1) at 10 A g(-1)). In addition, the synergistic effect from this hybrid structure has led to the significantly improved cycling stability of the NiO/G supercapacitor, which exhibits a superior cycling stability of 100-120% retention of specific capacitance after 1500 cycles. This approach may advance the design and implementation of hybrid nanostructures in high-performance reversible supercapacitors.