Interlacing Rod and Sphere Morphology of MnO2 in RGO/NiO/MnO2 Ternary Nanocomposites for Supercapacitive Applications

Abstract

Supercapacitors are promising energy storage devices. Herein a comparative study was carried out between two samples of reduced graphene oxide-infused binary metal oxides, in which the morphology of one of the metal oxides (Manganese oxide) is altered. MnO2 was synthesized in two morphologies namely nanorods and nanospheres. The two morphologies (rod and spheres) were separately composited with the as-synthesized cone-structured nickel oxide and sheets of reduced graphene oxide (rGO) and were subjected to various structural, functional, morphological, electrochemical characterizations etc. The morphologies and structures of the as prepared samples were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectrometer (XPS). The functional properties were determined using Fourier Transform Infra-Red (FTIR) Spectroscopy. The electrochemical performance of both the samples were analysed using Cyclic Voltammetry (CV), Galvanostatic Charge/Discharge (GCD) measurements and Electrochemical Impedance Spectroscopy (EIS) under electrolytes with different pH namely 1M Na2SO4(pH = 7) and 1M Na2CO3(pH = 11). The CV was analysed with different scan rates and GCD was taken under 1–5 Ag−1 current densities. The cycling stability of the materials were testified for 5000 cycles of CV and GCD. The results are discussed. The main advantage of this work is that the best suited morphology with better ion transfer rate having commendable electrochemical ability and long-standing cycle rate for a promising supercapacitor is identified which will serve as the reference for the future supercapacitor electrodes.