Hydrothermal synthesis of graphene oxide interspersed in non-uniform tungsten oxide nanorod and its performance towards highly efficient hybrid supercapacitor

Abstract

In this study, hybrid graphene oxide/tungsten oxide nanostructures (GO/WO3 NSs) are synthesized using an eco-friendly and efficient hydrothermal method. Physicochemical analysis reveals the presence of a monoclinic phase with characteristic diffraction peaks, as indicated by the crystallinity degree. Using a field emission scanning electron microscope, heterogeneous non-uniform agglomerated nanosheets with non-uniform nanorods are observed in the GO/WO3 hybrid NSs. Results of transmission electron microscopy and X-ray photoelectron spectroscopy provide comprehensive details regarding the morphological, structural, and electronic state characteristics of the GO/WO3 hybrid NSs. Electrochemical data for GO/WO3 are obtained using an aqueous 2 M KOH electrolyte. The maximum specific capacity (Csp) and gravimetric capacitance (Cg) of the GO/WO3 are observed under 10% GO. The values of Csp and Cg are 123 mAh/g and 738 F/g, respectively, whereas the maximum energy (Ed) and power densities (Pd) are 37 Wh/kg and 500 W/kg at 5 mA/cm2, respectively. Furthermore, the optimized sample (GO-W2) shows superior capacitive retention of 88% over 7000 cyclic voltammetry cycles at a scan rate of 100 mV/s. A GO-W2-NF//GO-NF (where NF represents Ni-foam) asymmetrical hybrid liquid state device is fabricated using a two-electrode system, which demonstrates favorable electrochemical properties, i.e., Csp and Cg values of 94 mAh/g and 213 F/g at 5 mV/s respectively, and Ed and Pd values of 25 Wh/kg and 1000 W/kg at 4 mA/cm2, respectively. These findings indicate that GO/WO3 hybrid NSs are effective electrode materials for future research pertaining to energy storage systems.