Electrochemical analysis of asymmetric supercapacitors based on BiCoO₃@g-C₃N₄ nanocomposites

Supercapacitors are gaining popularity these days because of their good cycle stability, superior specific capacitance, high power density, and energy density. Herein, we report the synthesis of bismuth cobalt oxide (BiCoO₃) combined with graphitic carbon nitride (g-C₃N₄) by the hydrothermal method. The BiCoO₃@g-C₃N₄ nanocomposite was well characterized using XRD, FE-SEM, FT-IR, and DRS-UV techniques. The supercapacitor properties of the BiCoO₃@g-C₃N₄ nanocomposite were then studied using cyclic voltammetry, galvanic charging-discharging, and impedance spectroscopy techniques. Due to the synergistic effect, BiCoO₃@g-C₃N₄ showed a high specific capacitance value of 341 F g^-1 at a current density of 1 A g^-1 and excellent retention of specific capacitance (98.82%) after 1000 cycles and a high power density of 1125 W kg^-1. Using the impedance spectroscopy technique, the charge transfer resistance of BiCoO₃, g-C₃N₄, and BiCoO₃@g-C₃N₄ was measured. BiCoO₃@g-C₃N₄ showed a low charge transfer resistance compared with BiCoO₃ and g-C₃N₄. The asymmetric supercapacitor (ASC) device was prepared using activated carbon (negative side) and BiCoO₃@g-C₃N₄ (positive side) electrodes. It showed a specific capacitance of 129 F g^-1 at 1 A g^-1, power density 2800 W kg^-1 and energy density 35 W h kg^-1. Finally, we conclude that, due to the high specific capacitance, good cycle retention, fast redox activity, and low charge transfer resistance BiCoO₃@g-C₃N₄ is a good electrode material for energy storage applications.