Facile microwave synthesis of Sn-doped WO₃ for pseudocapacitor applications

In the present work, we have successfully synthesized pure tungsten oxide (WO₃) and Sn (3 and 5 wt%)-doped WO₃ nanoparticles using facile microwave irradiation method and studied about the electrochemical performances for supercapacitor electrode material. Structural and morphological studies of the prepared nanomaterials were investigated systematically. The powder XRD analysis reveals that pure WO₃ and Sn-doped WO₃ have monoclinic crystal structure and also crystallite size of the material decreases from 38 to 30 nm with increasing dopant concentration. Micro-Raman analysis confirms the formation of monoclinic phase with υ(O–W–O) stretching and δ(O–W–O) bending mode of vibration. SEM and micrographs show the elongation of the plate-like nanostructure of WO₃ for the doping of Sn. High-resolution transmission electron microscope images depict the morphological change and increased porosity in doped samples. The supercapacitive performance and the electrochemical conductivity of the samples were analysed using cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy measurements. The results demonstrate that the 5 wt% Sn-doped WO₃ electrode has the enhanced electrochemical performance in 1 M KOH with a maximum specific capacitance of 418 F g⁻¹ at low current density of 1 A g⁻¹. Also, it shows the increase in energy density from 4.88 to 11.77 Wh kg⁻¹ with respect to the Sn concentration at the power density of 225 W kg⁻¹_.