Charge storage kinetics of MoS₂ flower decorated reduced graphene oxide for quasi solid-state symmetric supercapacitor

In this study, micro flower-like molybdenum disulfide (MoS₂) is directly grown on reduced graphene oxide (rGO) sheets by a new one-pot facile hydrothermal strategy with different MoS₂-rGO combinations (such as 1:1, 1:2 and 2:1, respectively). The structural and morphological study demonstrate that MoS₂ flowers are uniformly distributed on the rGO sheets. The capacitive performance of synthesized samples has been evaluated by various electrochemical techniques, using a three-electrode set-up in 1 M Na₂SO₄ electrolyte. The electrochemical results reveal that the MoS₂-rGO (1:2) offers the highest capacitance of 352 F g⁻¹ at a current density of 0.2 A g⁻¹. Further, the charge storage kinetics of MoS₂-rGO (1:2) electrode have been evaluated by in-depth analysis of the Cyclic Voltammetry (CV) profile, implying that the charge storage mechanism contributes to both capacitive and diffusion-controlled processes. Three symmetric supercapacitor (SC) devices are fabricated using three aforementioned compositions as the active material with polyvinyl alcohol (PVA)/Na₂SO₄ hydrogel membrane as the separator-less electrolyte. The symmetric SC device (MoS₂-rGO (1:2) || MoS₂-rGO (1:2)) based on MoS₂-rGO (1:2) as the electrode material demonstrates maximum capacitance value 256 F g⁻¹ at 0.15 A g⁻¹. This strategy to combine the appropriate amount of MoS₂ with rGO sheets has enhanced the electrochemical performance of MoS₂-rGO composite due to the formation of a hetero-interface between MoS₂ and rGO composite leading to fast ion propagation and facilitate the development of advanced quasi-solid-state energy storage devices.