Metal Sulfides and their Composites for Electrochemical Energy Storage Applications

Abstract

In current study, the metal sulfides such as molybdenum disulfide (MoS2), copper sulfide (CuS) and nickel sulfide (NiS) were synthesized by facile hydrothermal route and their nanocomposites with conducting carbon scaffolds (reduced graphite oxide and carbon nanotubes) were prepared by simple ultrasonic exfoliation approach. The synthesized materials were successfully studied by various characterization techniques. The structural, purity, surface morphological study and conductivity of obtained materials have studied by physicochemical techniques such as X-ray diffraction (XRD), fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), Brunauer-Emmett-Teller (BET) analysis and current voltage (I-V) measurements. Furthermore, the electrochemical properties of all prepared materials were explored by performing electrochemical measurements including cyclic voltammetry, cyclic charge/discharge and electrochemical impedance. To improve the electrical and electrochemical properties of MoS2 nanoarchitecture, we formed its nanocomposite (MoS2/r-GO) with 10% r-GO. After the addition of 10% r-GO, the nanocomposite showed the electrical conductivity of 1.24 × 10-1 Sm-1 that is higher than the pure MoS2 (2.2 × 10-7 Sm-1 ). The prepared nanocomposite also showed higher specific capacitance (441 Fg-1 at 1 Ag-1 ) than the pure MoS2 nanoarchitecture (248 Fg-1 at 1 Ag-1 ). The 2-D flake-like structure of the electrode increased its contact area with the r-GO matrix and electrolyte. The higher electrical conductivity and specific surface area of the nanocomposite facilitated the faradic and non-faradic charge storage mechanism. As the nanocomposite showed CV and CCD profiles in the negative potential window (-1 V to -0.53 V), therefore it has the potential to be used as a negative electrode material for hybrid supercapacitors applications. The observed results revealed the potential of the (MoS2/r-GO) nanocomposite-based cathode for hybrid supercapacitor applications. The nanocomposite of CuS with CNTs improved the electrical and electrochemical properties of CuS nanoarchitecture. The electrical conductivity of bare CuS was relatively less 1.85  10-4 Sm-1 compared to CuS/CNTs nanocomposite (2.34  104 Sm-1 ). The CuS/CNTs nanocomposite exhibited higher specific capacitance (422 F/g at 1 A/g) than the bare CuS nanoarchitecture (285 F/g at 1 A/g). The CuS/CNTs nanocomposite is missing 16.8% of its initial capacitance after 1000 charge-discharge xx cycles. To enhance the electrical conductivity and electrochemical properties of NiS nanoarchitecture were prepared the nanocomposites with conductive CNTs. The calculated electrical conductivity (σ) value for the NiS/CNTs sample comes to be superior (1.42  105 Sm-1 ) than that of the NiS sample (4.53  10-3 Sm-1 ), indicating a positive interaction among the NiS nanoparticles and CNTs. The NiS/CNTs nanocomposites revealed greater specific capacitance (732 Fg-1 at 1 Ag-1 ) than that of NiS@NF blank electrode (405 F/g). The NiS/CNTs nanocomposites have too much high cyclic stability and lost just 4.9% of its initial capacitance after 3000 charge discharge cycles