Alpha-Ni(OH)2 nanoflakes incorporated on MOF derived ZnO hybrid Faradaic arrays for high-performance asymmetric supercapacitor

Abstract

Elegant transition metal oxide nanocomposites with modified structures are required to enhance specific capacitance of supercapacitors. A core–shell embedded ZnO@Ni(OH)2 nanocomposite electrode with porous nano-flakes morphology has been synthesised by low temperature wet chemical method. Ni(OH)2 nano flakes are decorated on ZnO derived from Zeolitic Imidazolate Framework-8 (ZIF-8) by a facile technique. The wurtzite hexagonal phase of ZnO and α-Ni(OH)2 are evidenced by XRD analysis. FTIR spectral analysis confirms the Zn-O, Ni-OH and interlamellar hydrogen bonded Ni(OH)2 layers of the ZnO @Ni(OH)2 sample. FESEM and elemental mapping results reveal core–shell embedded architecture of ZnO@Ni(OH)2. The presence of primary elements such as Zn, Ni, and O of ZnO, Ni(OH)2 and their oxidation states are confirmed in XPS results with the existence of binding energies corresponding to Zn 2P3/2, Zn 2P1/2, Ni 2P3/2, Ni 2P1/2, and O 1s peaks. The ZnO@Ni(OH)2 nanocomposite electrode in a three electrode system exhibits a high specific capacitance of 510F g−1 at 1 A g−1 and a good cyclability for 2000 cycles at 10 A g−1 with 77% capacity retention. Also, in the case of an asymmetrical supercapacitor, it was delivered the specific capacitance of 45F g−1 at 1 A g−1. Furthermore, a good cyclability for 10,000 cycles with capacity retention of 76.25%, and a high power density of 1595.5 W kg−1 are obtained. The excellent electrochemical behaviour of ZnO@Ni(OH)2 nanocomposite favoured by the core–shell embedded architecture is discussed as a futuristic pseudocapacitor energy storage material.