Fabrication of cathode Bi2S3-rGO nanocomposites electrode for hybrid supercapacitors to enhance the energy storage properties

In this work, the two-dimensional Bi₂S₃-rGO nanocomposites have been successfully prepared through facile hydrothermal-assisted ultrasonication technique. The synthesized samples have been characterized for XRD, Raman, FESEM, EDX, HRTEM, SAED, XPS, and BET studies for studying their structure, vibrations, morphologies, purity, and chemical states. The CV analysis have been studied for fabricated Bi₂S₃ and Bi₂S₃-rGO NCs electrodes in three-electrode technique, in which the Bi₂S₃-rGO NCs electrode exhibits 247.8 C/g of excellent specific capacities in contrast to Bi₂S₃ electrode (76.0 C/g) at the appropriate scan rate of 10 mV/s, due to the synergistic effects of both Bi₂S₃ and rGO in hybrid electrode. The Bi₂S₃-rGO NCs electrode shows 296.7 C/g of total ($Q_T^{{\ast }^{\prime }})$, 171.6 C/g of inner ($Q_I^{{\ast }^{\prime }})$, and 125.0 C/g of outer ($Q_O^{{\ast }^{\prime }})$ specific capacities from Trasatti analysis. The EIS study provides the R_s and R_ct values of 0.65 and 1.30 Ω for Bi₂S₃-rGO NCs electrode, suggesting their good ion transportation characteristics. Also, the cyclic stability has been studied for Bi₂S₃-rGO NCs electrode and it provides 84.03 % of good capacitive retention and 104.31 % of coulombic efficiency over 3000 cycles. Additionally, the hybrid supercapacitor device (HSC) of Bi₂S₃-rGO//AC has been fabricated, which shows 110.1 C/g of specific capacity, 25.8 Wh/kg of energy density ($E_{\text{HSC}}$), and 844.9 W/kg of power density ($P_{\text{HSC}}$) at 1 A/g current density. Further, the fabricated device exhibits 86.3 % better capacitive retention and a coulombic efficiency ($\eta$) of 100.1 % at the current density of 10 A/g over 10,000 GCD cycles.