Microwave-assisted hydrothermal synthesis of NiO/Co3O4 nanosheets decorated on three-dimensional porous graphene for supercapacitors

Electrode material is the key part of capacitor, which seriously affects the electrochemical performance of supercapacitor. NiO/Co3O4 nanosheets decorated on three-dimensional porous graphene (NiO/Co3O4/3DGN) have been prepared though a microwave-assisted hydrothermal method. It is found that NiO can affect the crystallinity and morphology of Co3O4 in the composites. The composites possess excellent electrochemical performance with the special capacity of 1303.9 F g-1 (at 1 A g-1). The assembled NiO/Co3O4/3DGN//AC asymmetric supercapacitor device achieved an energy density of 18.8 Wh kg- 1 at a power density of 750.4 W kg- 1 and maintained 92.7% of the initial capacitance after 10,000 cycles. The excellent capacitance and rate capability of the composites can be attributed to its unique structural features. The large surface area and the rich porosity provide more activate sites and facilitate the fast diffusion of electrolyte during the charge/discharge process. The direct contact between NiO/Co3O4 nanosheets and 3DGN ensures effective charge transport.