3D porous graphene/NiCo2O4 hybrid film as an advanced electrode for supercapacitors

Graphene, as a family of 2D materials, can be used as film electrodes in energy storage devices because of its high surface area, electrical conductivity, and environmental stability. However, the pure graphene electrode attains aggregating nature, which significantly limits its practical application. To solve the overstacking problems, we construct a 3D porous reduced graphene (rGN) film by a novel and green Cu2O template-assisted route based on coordinating etching and precipitating process. Noticeably, a brand new material-NiCo2O4 is generated when the template is removed by optimizing the coordinating etchant and the reaction conditions. It is observed that NiCo2O4 perfectly imitates the shape of Cu2O template and has a hollow hydrangea-like structure. Furthermore, these emerging hollow NiCo2O4 hydrangeas not only prevent the re-accumulation of sheet layers, but also afford 3D porous structure for film, and greatly enhance the energy storage properties on account of the pseudocapacitance of NiCo2O4. The 3D graphene/NiCo2O4 film (3D rGN/NiCo2O4) exhibits high specific capacity of 708.36 F g(-1) at 1 A g(-1), remarkable rate performance of 582.11 F g(-1) even at 16 A g(-1), and superior circulation ability with 94.3% capacitance retention after 6000 cycles at 10 A g(-1), indicating the potential applications in energy storage.