Sustainable development of vanadium pentoxide carbon composites derived from Hibiscus sabdariffa family for application in supercapacitors†
For the future development of environmentally friendly and sustainable electrode materials, herein, novel orthorhombic vanadium pentoxide@carbon composites (V2O5@C–WHS, V2O5@C–R1HS and V2O5@C–R2HS) were synthesized via a green solvothermal process. According to the SEM and TEM analysis, the vanadium pentoxide@carbon (V2O5@C) composites exhibited a flower-like morphology with a few agglomerated nanoflakes located on their surface. The incorporation of carbon in the V2O5 matrix was established based on the element distribution mapping images, Raman spectroscopy, FTIR spectroscopy and XPS. The V2O5@C–R2HS composite presented the smallest thickness (40 nm) of the flower-like morphology and the highest content of carbon and V5+ ions. The electrochemical performance of all the electrode materials was studied in a three-electrode configuration using 6 M KOH aqueous electrolyte. The V2O5@C–R2HS composite electrode displayed the best electrochemical performance compared to that of the V2O5@C–WHS and V2O5@C–R1HS composites. The two-electrode configuration was evaluated using the V2O5@C–R2HS composite as the positive electrode and activated carbon as the negative electrode to fabricate an asymmetric device (V2O5@C–R2HS‖AC). The V2O5@C–R2HS‖AC device presented a specific energy and associated specific power of 33.4 W h kg−1 and 670 W kg−1, respectively, at 1 A g−1 and voltage of 1.6 V. The asymmetric cell showed excellent cycling stability of 98.9% coulombic efficiency and 88% capacity retention during a large number of cycles (25 000). Thus, the present study confirms that this novel green V2O5@C–R2HS composite exhibits a superior performance as a positive electrode for future sustainable supercapacitors.