Acid substitutions for WO3 nanostructures synthesis by the hydrothermal route and its effect on physio-chemical and electrochemical properties for supercapacitors
Umesh V. Shembade, Suprimkumar D. Dhas, Sunny R. Gurav, Rajendra G. Sonkawade, Sandeep B. Wategaonkar, Suhas R. Ghatage, Mayur A. Gaikwad, Jin Hyeok Kim, Vinayak G. Parale, Hyung‐Ho Park, A.V. Moholkar
Abstract
In this study, we have developed a feasible and eco-friendly electrode material for supercapacitor (SCs) application by effectively synthesizing different morphological structures of tungsten oxide nanostructures (WO 3 -NSs). The concentrated acids play a crucial role in the synthesis of WO 3 -NSs and are employed to evaluate the electrochemical activity. The stable phase formation and the crystal structures of WO 3 -NSs were confirmed by thermogravimetric and X-ray analysis. From the field emission scanning electron microscope (FE-SEM), the hexagonal-shaped nanosheets , one-dimensional nanorods (1D NRs), and heterogeneous non-uniform agglomerated nanosheets were observed for the WO 3 -NSs. The presence of functional groups and the stretching-bending vibrations of W O bonds were detected by Fourier transform infrared, and Raman spectroscopy respectively. The transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) offers a more in-depth morphological, structural, and elemental composition and electronic states investigation of the optimized WO 3 -NRs. Additionally, the electrochemical properties of the WO 3 -NSs have been examined in 1 M KOH electrolyte using Nickel Foam (NF) as a current collector. Furthermore, the M-WO 3 -NF electrode reveals higher specific capacity (Csp) and gravimetric capacitance (Cg) of 72 mAh/g and 600 F/g with high energy density (Ed) of 17 Wh/kg, and power density (Pd) of 321 W/kg as well as the superior Columbic efficiency (96.9 %) at 5 mA/cm 2 . The M-WO 3 electrode exhibits 91 % capacitive retention over 5000 cycles. The M-WO 3 -NF is used as the cathode and activated carbon (AC) as the anode in the design of an aqueous hybrid supercapacitor (AHSC) device. Notably, the M-WO 3 -NF//AC-NF device offers a Pd of 1060 W/kg at an Ed of 9 Wh/kg and remarkable electrochemical stability of 80 % over 3000 charge-discharge cycles. These results highlight the excellent electrochemical functionality and advantages of the M-WO 3 -NRs as a promising cathode for practical energy-storage systems.