Vanadium dioxide sulphur-doped reduced graphene oxide composite as novel electrode material for electrochemical capacitor

Abstract

In this study, vanadium dioxide (VO2) combined with sulphur-doped reduced graphene oxide (S-rGO) as a composite material is reported. Vanadium dioxide sulphur-doped reduced graphene oxide (VO2@S-rGO) composite was successfully synthesized via a rapid solvothermal technique by varying the S-rGO concentration on VO2. The structural, morphological, and textural properties revealed the successful integration of S into the rGO matrix, leading to a good interaction between S-rGO and VO2 in the composite materials. The optimized composite (VO2@S-rGO-1) presented better electrochemical performance and exhibits a specific capacitance of 204.2 F g−1 in 0.5 M K2SO4 electrolyte at a specific current of 0.5 A g−1 within a large stable potential window of 0.8 V vs Ag/AgCl. VO2@S-rGO-1 and cocoa-derived activated carbon (Cocoa-AC) were used as positive and negative electrodes, respectively, to fabricate an asymmetric supercapacitor device (VO2@S-rGO-1//Cocoa-AC). The device displayed excellent specific energy of 32.6 W h kg−1 with a corresponding specific power of 426.0 W kg−1 at 0.5 A g−1 in an operating cell voltage of 1.7 V. The stability test exhibited an excellent columbic efficiency of 99.9 % and capacitance retention of 75 % up to 10,000 galvanostatic charge/discharge at 10 A g−1. Overall, VO2@S-rGO-1//Cocoa-AC asymmetric device demonstrated excellent electrochemical properties and is thus a promising candidate for wide use in energy storage systems.