Electrocatalysis And Polymer Composites Based On Covalently Functionalized Molybdenum Disulfide

Molybdenum disulfide nanosheets(MoS₂)display many interesting properties and have a wide range of applications in the fields of energy storage,catalysis and composite materials etc.However,the surface of the original MoS₂ is inert and difficult to covalently functionalize,greatly limiting its application.In this thesis,we will explore the exfoliation,covalent functionalization and electrocatalysis of molybdenum disulfide nanosheets,as well as the preparation of nanocomposites upon polymer grafting.The specific research content includes the following aspects:1.The exfoliated MoS₂ nanosheets were obtained by solvent exfoliation,and then reacted in a naphthalene-sodium/tetrahydrofuran reductive system in an ice-water bath to render negatively electrified.Using methyl trifluoroacetate and trimethylsilyl iodide as grafting agents,acylated and silanized MoS₂ were obtained.Fourier transform infrared spectroscopy(FTIR)was used to characterize covalent functionalization of MoS₂,and the characteristic peaks of C-S and Si-S bonds were found.Thermogravimetric analysis(TG),X-ray diffraction(XRD),transmission electron microscopy(TEM),atomic force microscopy(AFM)and Raman absorption spectroscopy were used to investigate the phase structure,grafting rate and exfoliation of functionalized MoS₂.2.Different working electrodes were prepared to study the difference in electronegativity of acyl and silane MoS₂ nanosheets treated and the influence of sodium naphthalene reduction treatment on electrocatalytic activity,charge transfer and stability of MoS₂ nanosheets.X-ray photoelectron spectroscopy(XPS)proved that the functional groups were anchored on the surface of 2H phase MoS₂ nanosheets by means of chemical bonds.A three-electrode test system was used to perform linear sweep voltammetry(LSV),cyclic voltammetry(CV),electrochemical impedance(EIS)tests,and stability tests.The silanized MoS₂ nanosheets showed high catalytic activity(Tafel slope is 104 m V/dec),low charge transfer resistance(1.5?)and excellent hydrogen evolution stability,while the electrocatalytic activity of acylated MoS₂became worse.The electronegative functional groups on MoS₂either contribute to electron density or reduce electron density from nanosheets,thereby changing the electron transfer kinetics and electrocatalytic activity.3.Bromine-terminated polymethyl methacrylate(PMMA)was synthesized by atom transfer radical polymerization,which can react with negatively charged MoS₂produced by sodium naphthalene reduction treatment to prepare PMMA grafted MoS₂nanosheets(MoS₂-PMMA).FTIR,XPS and TG were used to characterize the chemical bonding and grafting rate of polymer modified MoS₂ nanosheets.AFM was used to characterize the microscopic morphology and dispersibility of MoS₂-PMMA nanosheets.PMMA was used as the matrix to composite with MoS₂-PMMA,and the composite material samples were prepared by solution casting method.TEM and SEM were used to study the dispersion,compatibility and interfacial interaction of MoS₂-PMMA in the polymer matrix,and the composite materials were subjected to tensile and thermal weight loss tests to observe the changes in its static mechanical properties and thermal stability.