Asymmetric supercapacitor performance of hydrothermally-synthesized MWCNT-WO3 composite electrode

Abstract

Supercapacitors are energy storage devices that have the potential to significantly contribute to meeting energy demands in the modern era. However, the charge storage capacity and stability of pseudocapacitive materials should be improved. To improve the electrode storage capacity, tungsten trioxide (WO3) has been synthesized and deposited on multi-walled carbon nanotubes (MWCNT-WO3) on stainless-steel substrates via hydrothermal technique. The structural, morphological, elemental, and compositional studies on WO3 and MWCNT-WO3 samples were done with X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform Infrared Spectroscopy (FTIR), contact angle, and Brunauer-Emmett-Teller (BET). The electrochemical features of the WO3 and MWCNT-WO3 materials were studied for supercapacitor application using a three-electrode set-up. The results obtained show highly crystalline films with porous nanoplates at the surface and monoclinic WO3 phase. The basic elemental constituents and chemical bonds present in the synthesized samples were confirmed using EDX and FTIR spectra. The MWCNT-WO3 exhibited an optimized capacitive behavior when compared to WO3. A specific capacitance of 818.31 Fg−1 was obtained at a scan rate of 5 mVs−1 in 0.5 M H2SO4 electrolyte. The composite MWCNT-WO3 was further used as an electrode in a solid-state asymmetric supercapacitor, PANI||MWCNT-WO3 fabricated with polyaniline (PANI) and MWCNT-WO3 as positive and negative electrodes in polyvinyl alcohol/sulphuric acid (PVA/H2SO4) gel electrolyte. The fabricated materials exhibited excellent electrochemical performance which makes them useful for supercapacitor applications.