Synthesis of vanadium dioxide and efficient strategy to improve its electrochemical performances as electrode materials for supercapacitor applications

In this work, vanadium dioxide was synthesized via a solvothermal process by using an electric oven. Vanadium dioxide (VO2), pseudocapacitive material, has several oxidation states and good specific capacitance as-compared to electrical double layer capacitor (EDLC) materials. However, it has a low electrical conductivity and lack of cycling stability. To improve vanadium dioxide supercapacitor performance, it is combined with reduced graphene oxide (rGO), EDLC material, to fabricate nanocomposite materials. rGO possesses a good electrical conductivity and high cycling stability, then a good material for enhancing VO2 electrochemical properties. Nevertheless, rGO is limited by the restacking of the nanosheets, which lowers its specific capacitance. Therefore, to prevent rGO from restacking, it was doped firstly using sulphur (S) and secondly using nitrogen (N) by adopting suitable strategies, effectively enhancing vanadium dioxide electrochemical performances as electrode material for supercapacitor applications. Structural, textural, morphological, and elemental mapping/composition properties were investigated by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption-desorption, field emission scanning electron microscope (FE-SEM), and energy dispersive X-ray spectroscopy (EDX) techniques to characterize the prepared materials. The electrochemical performances were evaluated through cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) in both three and two-electrode configurations using aqueous electrolytes.