Synthesis and electrochemical potentials of composite materials based on Cr_xV_2−xO/S–g–C₃N₄ for supercapacitor electrodes

A series of Cr_xV_2−xO₄ materials with varying ratios of vanadium and chromium (1:1, 0.75:1.25, 0.5:1.5, 0.25:1.75) and novel Cr_xV_2−xO₄ were synthesized. The co-incorporation of sulfur-doped graphitic carbon nitride (S–g–C₃N₄) with vanadium oxide and chromium for supercapacitor applications has not, as far as we are aware, been considered. Based on a comparative study of the XRD spectra, the produced nanocrystallites are of the monoclinic phase, with an average size of 67 nm. A very high specific capacitance of 554 F/g is shown by the Cr_{0. 25}V_1.75O₄-based electrode at a current intensity of 1 A/g, according to the CV, GCD, and EIS tests conducted in 2 M KOH aqueous electrolyte. Conversely, the composite 50% Cr_0.25V_1.75O₄@S–gC₃N₄-based electrode exhibits a specific capacitance of 717 F/g at 1 A/g current density. Accordingly, the addition of S–g–C₃N₄, which has an increased surface area and porosity, results in a larger specific capacitance of this new electrode material than the previous one. Furthermore, as shown by the EIS plots below, both the parent sample and the composite have low charge transfer resistance and high conductivity.