Effect of NiO/Ni(OH)2 nanostructures in graphene/CNT nanocomposites on their interfacial charge transport kinetics for high-performance supercapacitors

Abstract

Graphene sheet/multiwall carbon nanotube (GMC) and its composites with NiO and Ni(OH)2 are synthesized by microwave-assisted technique for the application of high-performance supercapacitor devices. In the present study, carbon nanotubes are used to improve the electrical conductivity and also to prevent the graphene layers from restacking. Moreover, these carbonaceous materials not only are contributing the electrical conductivity but also increase their active sites on composite surfaces. The as-prepared nanocomposites are characterized by powder X-ray diffraction, Raman spectroscopy, FTIR, and BET analyses. The morphological features are visualized by FESEM and HRTEM images that have apparently showed the decoration of GMC composite by Ni(OH)2 nanoparticles. XPS spectra reveal the chemical bond formation and oxidation states of Ni 2p, C 1s, and O 1s energy levels. The maximum specific capacitance of 1663 F g−1 for the corresponding current density of 1 A g−1 is realized in the GMC-Ni(OH)2 nanocomposite-based electrode. In addition, the cyclic stability seems to be good with 95.7% retention even at 2000 charge-discharge cycles. The fabricated asymmetric supercapacitor device delivers a maximum cell voltage of 1.8 V with high energy density (32.85 Wh kg−1) and high power density (3196 W kg−1) at the current density of 4 A g−1. Thus, GMC-Ni(OH)2 nanocomposite is proven to be a promising candidate as active electrode material for high-performance supercapacitor device applications.