Probing the influence of morphological transformation on the electrochemical properties of hydrated tungsten oxide (WO3−x·H2O) for a high-rate aqueous asymmetric supercapacitor

Abstract

The present study aims to probe morphological tuning of hydrated tungsten oxide (WO_3−x·H₂O) nanostructures and investigate their electrochemical performance for energy storage in supercapacitors. The WO_3−x·H₂O nanostructures have been prepared via a single-step wet chemical method. Furthermore, a morphological transition of WO_3−x·H₂O nanostructures from nanosheet-assembled nanoflowers (W1) to nanoribbons (W2) as a result of regulating the reaction time has been achieved without disturbing the orthorhombic crystal structure. The morphological transformation from W1 to W2 exhibited a decrease in crystallinity and other physical properties, significantly affecting electrochemical behavior. Electrochemical investigations revealed that W1 has a higher specific capacitance (70 F g⁻¹) than W2 (37 F g⁻¹) at a current density of 1 A g⁻¹. Moreover, an aqueous asymmetric supercapacitor (AASC) device was fabricated using WO_3−x·H₂O as the negative electrode. The device exhibited a specific capacitance of 40 F g⁻¹ at 0.5 A g⁻¹ with an energy density of 12.5 W h kg⁻¹ and a power density of 3784 W kg⁻¹. Additionally, it demonstrated excellent cycling stability with 97% capacitance retention over 5000 cycles. These findings highlight the potential of morphology-controlled WO_3−x·H₂O nanostructures for advanced energy storage applications.