Synergistic behavior of vanadium pentoxide-carbon sphere electrocatalyst towards iron-based redox flow battery and supercapacitor applications

In this paper, the multifunctional, electron-rich, unique structured vanadium pentoxide-carbon sphere (V2O5-CS) composite was used as a catalyst for energy storage devices such as iron-based redox flow batteries (IRFBs) and supercapacitors. The V2O5-CS composite was synthesized using a single-step hydrothermal method and it was found to have a nano flake-like structure deposited on the surface of spheres. The collective synergistic effect offered by V2O5 and CS in V2O5-CS enables easy flow of electrons and hence improves the reversibility, faradaic redox reaction and stability of the material. The electrocatalytic activity of the composite towards IRBF was tested to analyze the kinetic reversibility and electrode-electrolyte resistance. The charge-discharge and life-cycle studies were carried out to evaluate the stability of the electrode. V2O5-CS modified graphite felt (V2O5-CS GF) electrode was stable up to 50 cycles and the cell resulted in coulombic efficiency (CE) of 89 %. The composite along with V2O5 and CS were coated on Toray carbon electrodes were tested for supercapacitor using CV, EIS, and galvanostatic charge-discharge (GCD) to calculate the specific capacitance (Cs) offered by the material to the variation of voltage and current density applied. The V2O5-CS resulted in a specific capacitance of 612 F/g at 5 A/g and it has been found to have specific capacitance retention of 58 % up to 1500 cycles at a current density of 10 A/g. This is a pioneering work to present V2O5-CS composite as an efficient, peculiar electrocatalyst for energy storage devices.