The hetero-structured nanoarray construction of Co3O4 nanowires anchored on nanoflakes as a high-performance electrode for supercapacitors

Abstract

The successful synthesis of a self-supported 3D hetero-structured Co3O4 array on Ni foam under hydrothermal conditions is described herein. In this unique nanoarray structure, the Co3O4 nanowires are anchored onto the surface of Co3O4 nanoflakes, which effectively enlarge the surface area, provide rich active states for the Faraday redox reaction and promote the diffusion rate of the electrolyte ions. The super-capacitive performance of the hetero-structured Co3O4 array is shown to be easily optimized by altering the hydrothermal reaction time to control the integration of the Co3O4 nanowires onto the surface of the nanoflakes. As expected, the hetero-structured Co3O4 array synthesized using a hydrothermal time of 8 h exhibits remarkable super-capacitive performance, such as a high specific capacitance of 2053.1 F g−1 and a high rate capability. Further, the hybrid supercapacitor device assembled using the hetero-structured Co3O4 array and graphene has an energy density of 22.2 Wh kg−1 and outstanding cycle stability. The capacitance retention is up to 93.3% after 10,000 cycles, demonstrating the great potential of the Co3O4 array for supercapacitor application. This work also provides a better strategy for enhancing the charge storage capacity of the metal oxides.