Synergistic effect of redox couple VO2+/VO2+ with H3PO4 to enhance the supercapacitor performance

The purpose of this paper is to give a comprehensive study on the effect of redox additive (VOSO4) and the properties of supercapacitor. In this study, for the electrode of supercapacitor, carbon based material (synthesized from eucalyptus leaves) is used. This electrode material is characterized by using the X-ray diffraction, Raman spectroscopy, scanning electron microscopy and Fourier transform infrared spectroscopy techniques that confirm its well porous structure in graphitic conducting phase and its ability to use as an electrode material. Fabricated supercapacitor cells, by using H3PO4 and H3PO4 added VOSO4 electrolytes, are tested with electrochemical impedance spectroscopy, cyclic voltammetry and charge-discharge techniques. The cell consisting H3PO4+VOSO4 has provided 5-6 times higher capacitive performance than what observed with its pristine H3PO4 counterpart. The maximum specific capacitance and energy detected using H3PO4 were 117.6 F g(-1) and 8.6 Wh kg(-1) whereas the same parameters were found 704.1 F g(-1) and 52.2 Wh kg(-1), respectively for the VOSO4 based system. Maximum specific power, so it was also obtained higher (9.2kWkg(-1)) for redox system than the pristine one (7.9kWkg(-1)). The credit for this performance goes to the VO2+/VO2+ redox couple as well as the functional groups present in the active material. Furthermore, the cycle life, open circuit potential and thermal effects have been explored for the fabricated cells and in all those tests VOSO4 based redox system got succeed to leave its ample effect on the supercapacitor performance, positively.