Electrode materials with high surface area, tailored pore size, and efficient capability for ion insertion and enhanced transport of electrons and ions are needed for advanced supercapacitors. In the present study, a mixed metal-organic framework (MOF) (cobalt- and manganese-based MOF) was synthesized through a simple one-pot solvothermal method and employed as the electrode material for the supercapacitor. Notably, a Co-Mn MOF electrode displayed a large surface area and excellent cycling stability (over 95% capacitance retention after 1500 cycles). Also, superior pseudocapacitive behavior was observed for the Co-Mn MOF electrode in the KOH electrolyte with an exceptional areal capacitance of 1.318 F cm. Moreover, an asymmetric supercapacitor was assembled using Co-Mn MOF and activated carbon electrode as positive and negative electrodes, respectively. The fabricated supercapacitor showed a specific capacitance of 106.7 F g at a scan rate of 10 mV s and delivered a maximum energy density of 30 W h kg at 2285.7 W kg. Our studies suggest the Co-Mn MOF as promising electrode materials for supercapacitor applications.

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The unique 3D network-like cobalt oxide architecture was electrochemically deposited on nickel oxide nanoworms (NiONWs) with nickel foil (NF) substrate. After the anodic polarization of NF and its activation, a very thin film of NiO nanoworms with the average diameter of 30 nm and the length of 100 nm was successfully grown on anodized Ni foil (a-NF) by using a facile hydrothermal method under the mild conditions including a saturated alkaline solution of Ni 2+ at 65 ˚C to prepare a-NF/NiONWs. Then, 3D network-like Co3O4 nanosheets with the average thickness of 25 nm were directly electrodeposited on a-NF/NiONWs by using cyclic voltammetry under the optimized experimental conditions. The morphologies and detailed geometrical structures of the electrodes were conducted by FE-SEM. The fabricated a-NF/NiONWs/Co3O4 electrode provides a high areal specific capacitance of 1320 mF cm-2 at a current density of 4 mA cm-2 and high mass specific capacitance of 2000 F g-1 at the current density of 6 A g-1. By using a-NF/NiONWs/Co3O4 as a positive electrode and reduced graphene oxide-deposited NF (RGO/NF) as a negative electrode, a solid-state asymmetric a-NF/NiONWs/Co3O4//RGO/NF supercapacitor was assembled and it exhibited a high specific capacitance of 471.4 mF cm-2 at a current density of 3 mA cm-2. The fabricated solid-state supercapacitor also showed good rate capacity and long-term cycling performance of 2000 cycles.

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