Sustainable development of vanadium pentoxide carbon composites derived from Hibiscus sabdariffa family for application in supercapacitors

For future development of environmentally friendly and sustainable electrode materials, novel orthorhombic vanadium pentoxide@carbon composites (V2O5@C-WHS, V2O5@C-R1HS and V2O5@C-R2HS) were synthesized using a green solvothermal process. From the SEM and TEM analysis, vanadium pentoxide@carbon (V2O5@C) composites materials shown flower-like morphologies with the smallest agglomerated nanoflakes on the surface. The incorporation of carbon into the V2O5 matrix was established from the element distribution mapping images, Raman, FTIR and XPS methods. The V2O5@C-R2HS composite presented the smallest thickness (40 nm) of the flower-like morphology and the highest amount of carbon and V5+ ions. The electrochemical performance of all the electrodes materials was studied in three-electrode configurations using 6 M KOH aqueous electrolyte. The V2O5@C-R2HS composite electrode displayed a better electrochemical performance than V2O5@C-WHS and V2O5@C-R1HS composites. A two-electrode configuration was evaluated using the V2O5@C-R2HS composite as a positive electrode and an activated carbon as a negative electrode to fabricate an asymmetric device (V2O5@C-R2HS//AC). The V2O5@C-R2HS//AC device presented a specific energy and an associated specific power of 33.4 W h kg-1 and 670 W kg-1, respectively at 1 A g-1 in a voltage of 1.6 V. The asymmetric cell showed excellent cycling stability of 98.9% coulombic efficiency and 88% capacity retention up to a large number of the cycles (25.000). This study confirmed that this novel green V2O5@C-R2HS composite can ensure far better performance as a positive electrode for future sustainable supercapacitors.