Harnessing the electrochemical ability of a Ce4O4S3/Ni3S2 composite as an electrode for a symmetric supercapacitor

Abstract

Transition-metal chalcogenides and rare-earth elements are extensively used in energy storage applications as electrode materials because of their good electrical conductivity, thermal and mechanical stability, and flexibility. In this study, cerium oxysulphide/nickel sulphide [Ce₄O₄S₃/Ni₃S₂] (CSNS) composites were synthesized by a hydrothermal method using cerium and nickel at three different metal ratios, represented as CSNS (1 : 1), CSNS (1 : 2), and CSNS (2 : 1). XRD analysis of the prepared materials confirmed the formation of a Ce₄O₄S₃/Ni₃S₂ composite crystal structure. SEM analysis revealed aggregated clusters of rod-shaped, sphere-shaped, and non-uniform granules for CSNS (1 : 1), (1 : 2), and (2 : 1), respectively. XPS analysis of the CSNS (2 : 1) composite revealed binding energies of 168 eV, 531.25 eV, 855.69 eV, and 885.76 eV, attributed to S 2p, O 1s, Ni 2p, and Ce 3d elements, respectively. The aggregation of the granules was confirmed by transmission electron microscopy (TEM) for CSNS (2 : 1). BET analysis indicated a mesoporous material, with the highest surface area (39.89 m² g⁻¹) and pore diameter (40.63 nm) observed for the CSNS (2 : 1) composite among all the prepared samples. The electrochemical properties of the materials were assessed using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) analysis, and electrochemical impedance spectroscopy (EIS). A symmetric supercapacitor device was fabricated with the CSNS (2 : 1) composite that showed a high specific capacitance of 67 F g⁻¹, a specific energy of 18 Wh kg⁻¹, and a specific power of 1399 W kg⁻¹ at a specific current of 0.5 A g⁻¹. Furthermore, the device withstands up to 5000 cycles, shows 99% coulombic efficiency and 85% capacitance retention.