Design, synthesis and evaluation of three-dimensional Co3O4/Co3(VO4)2 hybrid nanorods on nickel foam as self-supported electrodes for asymmetric supercapacitors

Abstract

A novel self-supported electrode of three-dimensional Co3O4/Co3(VO4)2 hybrid nanorods on the conductive substrate of nickel foam have been designed and synthesized by the combination of hydrothermal synthesis and subsequent annealing treatment. Based on the morphology, a possible mechanism is proposed. The unique nanostructure has been served as an “ion reservoir” to infiltrate between the electrode surface area and the electrolyte, which can ensure the ion/electron transfer. And the powerful distribution of electric field on nanorods makes the surface in response the electrode reaction as completely as possible. The electrode manifests satisfying capacitance of 847.2 F g−1, outstanding rate capability and excellent cycling stability. Also, an asymmetric supercapacitor has been assembled, where Co3O4/Co3(VO4)2 and activated carbon acted as the positive and negative electrodes respectively, and the maximum specific capacitance of 105 F g−1 and the specific energy of 38 Wh kg−1 are demonstrated at a cell voltage between 0 and 1.6 V, exhibiting a high energy density and stable power characteristic.