Investigating the synergistic effect of hybridized WO3-ZnS nanocomposite prepared by microwave-assisted wet chemical method for supercapacitor application

Abstract

Several authors reported that the naked tungsten oxide (WO3) is basically poor in capacitance. In this report, we have made an attempt to enhance the capacitive performance of WO3 through compositing. The different ratios of ZnS (2wt%, 4wt%, 6wt%) was loaded with WO3 and hybridized WO3-ZnS nanocomposites were prepared by the microwave-assisted wet chemical method. The XRD analysis revealed the mixed state of the orthorhombic and monoclinic structure of WO3. In addition to that, some peaks corresponding to the cubic structure of ZnS was also observed. The average particle size was calculated as ±19nm. Microscopic studies like SEM and HRTEM analysis revealed that as-prepared nanocomposites consisted of irregular particles of relatively uniform size. The existences of functional groups are analyzed using FTIR and confirmed the chemical bonding nature and the phase shift between WO and Zn. The TGA/DTA analysis shows that as the prepared structure is stable up to 400°C temperature afterwards gradual weight loss was started. Finally, the electrochemical properties have been investigated in H2SO4 and KOH electrolyte by cyclic voltammetry and galvanic charge-discharge analysis. The maximum specific capacitances of as-synthesized samples were calculated as 44F/g, 105F/g, 120F/g and 215F/g correspondingly for the WO3 (a) particle and hybridized WO3-ZnS (b, c, d) nanocomposites in 20% KOH electrolyte. Similarly, in H2SO4 electrolyte, bare WO3 showed maximum capacitance of 246F/g and WO3-ZnS (d) exhibited a maximum capacitance of 17F/g, whereas remaining samples exhibited less than 10F/g. The long cyclic analysis showed that coulombic efficiency of WO3-ZnS composite in KOH electrolyte is more than 100% up to 4000cycles and capacitance retention is 71%.