Tungsten oxide/reduced graphene oxide composite electrodes for solid-state asymmetric supercapacitor application

Tungsten oxide (WO3) thin films were deposited on flexible stainless steel (SS) substrates via low-cost chemical bath deposition (CBD) method by varying concentration of sodium tungstate precursor (0.05–0.2 M). Also, tungsten oxide/reduced graphene oxide (WO3/rGO) nanocomposite thin films were deposited (0.15 M sodium tungstate precursor concentration) at different rGO concentration variations (0.5, 1, and 1.5 mg mL−1). The effect of precursor concentration and rGO addition on the physicochemical properties of electrodes was studied. The thin films of WR2 (deposited at 0.15 M sodium tungstate and 1 mg mL−1 rGO concentration) nanocomposites exhibited a hexagonal crystal structure along with a surface morphology resembling nanorods. The appearance of rGO in WO3/rGO was proved from the FT-IR, RAMAN, and EDAX studies. WR2 nanocomposite thin film exhibited 1060 F g−1 specific capacitance at scan rate of 5 mV s−1. The flexible WR2//PVA-H2SO4//activated carbon asymmetric (ASC) device was fabricated using WR2 as a negative electrode and activated carbon as a positive electrode which showed a specific capacitance of 175 F g−1 with energy and power densities of 19.1 Wh kg−1 and 0.43 KW kg−1, respectively, with 81.3% capacitive retention over 5000 CV cycles.