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

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 (2 wt%, 4 wt%, 6 wt%) 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 ±19 nm. 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 W–O 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 44 F/g, 105 F/g, 120 F/g and 215 F/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 246 F/g and WO₃-ZnS (d) exhibited a maximum capacitance of 17 F/g, whereas remaining samples exhibited less than 10 F/g. The long cyclic analysis showed that coulombic efficiency of WO₃-ZnS composite in KOH electrolyte is more than 100% up to 4000 cycles and capacitance retention is 71%.