A controllable top-down etching and in-situ oxidizing strategy: metal-organic frameworks derived α-Co/Ni(OH)2@Co3O4 hollow nanocages for enhanced supercapacitor performance

The rational design and controllable fabrication of functional heterostructure consisting of capacitive framework and insertion is recognized as an efficient strategy to develop electrode materials for enhanced supercapacitor performance. In this work, a controllable NaH2PO2 etching and in-situ O2 oxidation process is developed, and a series of Co3O4 embedded α-Co/Ni(OH)2 hollow nanocages are successfully constructed via metal-organic frameworks (ZIF-67) as template. The optimized heterostructure (α-Co/Ni(OH)2@Co3O4-70) effectively take the advantages of each component that rich electrolyte diffusion channels and abundant reaction active sites of α-Co/Ni(OH)2 species, as well as excellent conductivity and stability of Co3O4 species. Therefore, a high capacitance value of 1000 F g−1 at 1 A g−1 and excellent ratio performance of 74% capacitance retained from 1 A g−1 to 10 A g−1 is achieved. Meanwhile, the hybrid nanocages present an enhanced cycling stability of retaining its 72.34% original capacitance after 8000 charge-discharge cycles. Furthermore, the as-assembled α-Co/Ni(OH)2@Co3O4-70//AC device exhibits a high energy density of 23.88 W h kg−1 at a power density of 0.075 kW kg−1.