High-Energy-Density Supercapacitors Based on WO3/rGO Nanocomposite Electrodes with PVA/KOH Gel Electrolyte

Abstract

This study explores high-energy-density supercapacitors based on tungsten trioxide/reduced graphene oxide (WO3/rGO) nanocomposites synthesized via a microwave-assisted method. Although supercapacitors offer fast charge–discharge, long cycle life, and high power density, their limited energy density remains a challenge. WO₃ provides abundant redox activity but suffers from poor conductivity, while reduced graphene oxide (rGO) offers high conductivity but limited capacitance. Integrating the two materials yields a synergistic effect that enhances electrochemical performance. WO3/rGO nanocomposites were prepared by dispersing GO with WCl₆ under microwave irradiation, followed by composite formation. Structural analyses using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and field-emission scanning electron microscopy (FESEM) confirmed the reduction of GO, homogeneous dispersion of WO3 nanoparticles (~22 nm), and the formation of polycrystalline WO3 domains on rGO sheets. Electrochemical evaluation was conducted with a 2 M PVA/KOH gel electrolyte in a solid-state configuration. The WO₃/rGO electrode achieved a high specific capacitance of 697.29 F·g⁻¹, energy density of 24.21 Wh·kg⁻¹, and power density of 2,258.06 W·kg⁻¹. It also maintained ~651 F·g⁻¹ after 5000 cycles, demonstrating excellent stability. These results highlight WO3/rGO nanocomposites as promising electrode materials for flexible and environmentally sustainable supercapacitors.