Electrochemical behaviour of ternary MoS₂/rGO heterostructure and PPyNTs nanocomposites for supercapacitor electrode

Reduced graphene oxide (rGO) and molybdenum disulphide (MoS₂) are two dimensional materials used as charge storage electrode materials. MoS₂-rGO heterostructures have been synthesized by self-assembly of positively charged MoS₂ nanosheets with negatively charged graphene oxide (GO) nanosheets in varying ratios. GO was reduced by hydrothermal route without using any reducing agent. MoS₂-rGO heterostructures were synthesized in 3 different ratios of 1:2, 1:1, and 2:1. MoS₂-rGO/PPyNTs nanocomposite was prepared by adding 40 wt% of MoS₂-GO nanocomposite in pre-synthesized PPyNTs followed by hydrothermal reduction of GO. Structure and morphology of the nanocomposites were characterized by SEM, TEM, XRD, FTIR and TGA. Further, electrochemical properties of the nanocomposites were evaluated with cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). Capacitive response is found to be highest for the 1:1 MoS₂-rGO/PPyNTs/ITO electrode. 1:1 MoS₂-rGO/PPyNTs/ITO ternary electrode delivers enhanced specific capacitance of 1561 F g⁻¹ at 1 A g⁻¹ current density and specific capacitance of 786 F g⁻¹ (50% of capacitive retention) at 15 A g⁻¹ exhibiting an excellent rate performance. 1:1 MoS₂-rGO/PPyNTs/ITO ternary electrode exhibits 76 % of cycling stability after 5,000 charge-discharge cycles at 10-fold of current density. (paper)