In situ construction of multi-dimensional Co3O4/NiCo2O4 hierarchical flakes on self-supporting carbon substrate with ultra-high capacitance for hybrid supercapacitors

Research on environmentally friendly energy storage devices is an important strategy to solve the energy crisis and environmental pollution. Herein, a novel self-supporting electrode based on multi-dimensional Co3O4/NiCo2O4 hierarchical flakes coating on graphene/carbon sphere (rGO/CS) conductive substrate is reasonably designed. Firstly, a simple hydrothermal method is used to synthesize NiCo2O4 with both flake and nanoneedle morphology on the rGO/CS substrate. Subsequently, Co3O4/NiCo2O4@rGO/CS is obtained by in-situ growth of metal organic frameworks polyhedrons on the surface of NiCo(2)Z(4) flakes followed by calcination. In the unique structure, benefitting from the synergy between the substrate and multielement transition metal oxides, the integrated film shows good conductivity, high specific surface area and abundant active sites. Thus, the binder-free electrode exhibits an ultra-high specific capacitance of 3876.6 F g(-1) (538.4 mA h g(-1)) at 1 A g(-1). A hybrid supercapacitor is assembled with activated carbon as the negative electrode and Co3O4/NiCo2O4@rGO/CS as the positive electrode, the device shows a highest energy density of 56.5 Wh kg(-1) at a power density of 800Wkg(-1). After 6000 charge-discharge cycles, 92.5% of the initial capacitance can be still maintained, indicating its good application prospects in energy storage materials. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

The research focuses on a novel self-supporting electrode based on multi-dimensional Co3O4/NiCo2O4 hierarchical flakes coating on graphene/carbon sphere (rGO/CS) conductive substrate. The electrode demonstrates good conductivity, high specific surface area, ultra-high specific capacitance, and high energy density, with stable cycling performance over a long period. These results indicate promising applications in energy storage materials.