Preparation And Characterization Of MoS₂/Graphene Composites And Its Electrochemical Properties

In recent years, graphene have lots of the unique physicochemical properties: quantum tunnel effect, ambipolar electric field effect, large theoretical specific surface area, super strength, excellent thermal conductivity, good light permeability, high Young’s modulus and extraordinary electron transport property. As a representative of transition-metal chalcogenide semiconductors, Mo S2 is composed of three atom layers(S-Mo-S) stacked together by weak van der Waals interactions. Mo S2 materials also have received increasing attention analogous to graphene, which is extensively applied in many fields such as catalysts, electrochemical biosensor, Li-ion rechargeable batteries, supercapacitors and optical device. Therefore, the article has successfully prepared molybdenum disulfide and graphene composite materials by a simple hydrothermal method with the morphology of the controllable. The crystal structure and microstructure of the composites are characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), and Raman spectroscopy. The electrochemical performances of the composites and the different components are studied using charge-discharge test, cyclic voltammograms test methods, and so on.(1) Graphene is firstly synthesized from graphite according to Hummers and Offeman method using graphite as raw materials. Au nanoparticles(NPs) decorated graphene(Gr) composites are prepared by the microwave hydrothermal techniques. Au NPs with the diameter of 20 nm are uniformly bestrewed and not aggregated on the surface of the Gr sheets. The resulting biosensor displays a high sensitivity, good reproducibility, long-time stability, wide linear range from 0.1-70μmol·L-1 and low limit of detection with 0.03μmol·L-1(based on the S/N=3) for the detection of H2O2. Thus, the Nafion/Hb/Au NPs-Gr biosensors can be served as a novel biosensor for H2O2 detection.(2) The flower-like Mo S2 microspheres self-assembled by bent flakes is prepared and studied by a routine hydrothermal method using thiourea and sodium molybdate as starting materials. Flower-like Mo S2 microspheres are employed to immobilize hemoglobin(Hb) in order to fabricate a novel biosensor. The electrochemical properties of the designed Nafion/Hb/Mo S2/GC electrode are investigated by the cyclic voltammograms(CVs). The experimental results show that the resulting biosensor displays a high sensitivity, good reproducibility and long-time stability, and the wide linear range and detection limit are 2-128μmol·L-1 and 0.6μmol·L-1 for the detection of H2O2. The preparation methods of flower-like Mo S2 microspheres can not only lay a solid foundation for the preparation of the graphene-based composites, but also is a good way to guide follow-up experiments smoothly.(3) Mo S2-Gr composites are prepared by a simple one-pot hydrothermal method using graphene oxides as substrate. And the prepared process is studied for flower-like Mo S2 microspheres directly in the growth of graphene surface. Mo S2-Gr composites are employed to immobilize hemoglobin(Hb) in order to fabricate a novel biosensor. Compared with the electrochemical properties of the Nafion/Hb/Mo S2-Gr/GC and Nafion/Hb/GO/GC electrodes, the Nafion/Hb/ Mo S2-Gr biosensors display a uppermost electrocatalytic property, as well as a high sensitivity, good reproducibility and long-time stability, which show the wide linear range and detection limit for the detection of H2O2. Therefore, it has the very good development prospect in the field of electrochemistry.(4) Gr@Mo S2 composites are prepared by a simple one-pot hydrothermal method using H2 O and ethyl alcohol as solvent. Meanwhile, Gr@Mo S2 composites as an anode materials are studied for the electrochemical performance of lithium-ion batteries. The results show the initial discharge capacity of 1296 m Ah g-1. At the condition of the current density of 100, 300, 500 and 1000 m A·g-1, the discharge capacity of the Gr@Mo S2 composites are 768(current density of 100 m A·g-1), 475, 315 and 152 m Ah·g-1, respectively. After a large current charging process, Gr@Mo S2 composites can still retain the discharge capacity in 709 m Ah·g-1(current density of 100 m A·g-1). This kind of composites show high discharge capacity, good stability and reversible charge-discharge cycle performance. the Gr@Mo S2 composites will also have more extensive application prospects in electrochemical fields.