Synergistic ultrasound and microwave synthesis of WO3 nanostructures for dielectric and supercapacitor performance

Abstract

Microwave and ultrasound irradiation are two non-conventional types of energy that have been used to advance the field of inorganic nanomaterial synthesis, as these sources enable the production of enhanced synthetic efficacies, as well as environmental friendliness. In this study, we describe how we created WO₃ nanostructures using a new method that combines ultrasound and microwave energy for use in supercapacitors and dielectric devices. X-ray diffraction also confirmed a highly crystalline orthorhombic WO₃ structure. In contrast, SEM and FESEM microscopy revealed nanorod and nanosheet morphologies that formed amalgamated structures with an average crystalline size of 19–24 nm. The purity and composition of the synthesised material were confirmed by EDAX. Electrochemical measurements showed that the sample prepared with 5 min of ultrasonic irradiation had the highest specific capacitance of 252 F/g, with exceptional capacitance maintenance of 100 % after 3000 charge-discharge cycles, much greater than values that were previously reported for WO₃ synthesised by conventional hydrothermal or microwave-only processes (generally 44–200 F/g and lower retention). Dielectric results provided a dielectric constant of 6.88–14.16 at 1 kHz (40–100 °C) and an increase in AC conductivity with increasing frequency and temperature. Synergistic combinations of ultrasound and microwave irradiation yielded better crystallinity, agglomeration synthesis methods. This paper shows that using ultrasound with microwave-assisted WO₃ nanostructures can lead to better uses in future energy storage and dielectric-related applications.