Heterostructure cadmium sulfide/reduced graphene oxide/ zeolitic imidazolate framework-8 ternary nanocomposite as cathode material for high performance asymmetric supercapacitor device

Zeolite-structured metal-organic frameworks (MOFs) and their composites are widely used in the energy saving and environmental sectors because of their larger surface areas, porous nature and electroactive organic counterparts. A simple in-situ growth is employed for designing a heterostructure composite using zeolite imidazolate framework-8 (ZIF-8), cadmium sulfide (CdS), and reduced graphene oxide (rGO). The prepared ZIF-8/CdS/rGO heterostructure composites have been evaluated using FE-SEM, HR-TEM, BET, and XPS studies to evaluate their structural, morphological, porosity and chemical compositions. HR-TEM suggests that ZIF-8 has been uniformly encapsulated by CdS and rGO. The electrochemical performance has been investigated with KOH and redox additive electrolyte (RAE) in a three-electrode configuration. The specific capacitances were found to be 514.64 F g −1 (KOH) and 1380.55 F g −1 (RAE), and the specific capacitance has been enhanced in the combined contributions of the electrode material and the reversible Fe(CN) 6 3− /Fe(CN) 6 4− redox couple with KOH. The designed ZIF-8/CdS/rGO electrode has excellent cyclic stability, with 87.32% capacity retention after 10000 cycles. The fabricated asymmetric supercapacitor device ((ZIF-8/CdS/rGO)//AC) demonstrated good capacitive performance over a broad potential window of 0 to 1.7 V, achieving a specific capacitance of 57.38 F g −1 and capacitance retention of 88.72%. The designed ASC device has series resistance values of 0.501 Ω and 0.553 Ω before and after 10,000 GCD cycles. According to the electrochemical results for ZIF-8/CdS/rGO, this material represents considerable potential for energy-efficient applications in sustainable and clean energy systems.