Synthesis Of Three Kinds Of Semiconductor Nanomaterials Including MoS₂ And Their Application In Photoelectrocatalysis And Analysis

In this thesis,based on the successful preparation of MoS₂,Au-MoS₂,Cu₂O/TiO₂/graphene composite nanomaterials,various characterization techniques are used to to analyze the morphology,structure and properties of the prepared materials,including X-ray powder diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,Scanning electron microscopy（SEM）,Raman spectra（Raman）,Transmission electron microscopy（TEM）,electrochemical methods,and so on.Also,the applications of the materials inphotoelectrocatalysisand analysis are further explored.The main contents include:1.In this section,molybdenum disulfide（MoS₂）nanostructures with different morphologies have been prepared via a hydrothermal process.Theirmorphology and structure are characterized with TEM,SEM and XRD.After being modified on glassy carbon electrodes,the catalytic hydrogen evolution of the composites are investigated in 0.5M H₂SO₄ by using linear sweep voltammetry（LSV）and Tafel plot analysis.The results show that the catalytic performance is dependent of the morphology.Moreover,electrochemical detection of hydroquinoneis studied based on this composite by the current-time curve（I-t）method.It is found that a linear response beteween the current and its concentration（c）,and the linear equation can be expressed as: I = 0.1394 + 1.0636c（R² = 0.99608）,where the sensitivity reaches 120μAmM^-1cm^-2with the detection limit of 3.2×10^-7 mol/L（S/N = 3）.Besides,the recovery experiment of hydroquinone was carried out on the Yellow River water sample with the satisfactory results.2.In the MoS₂-HAuCl₄ system,Au nanoparticles（AuNPs）are reduced and loaded on monolayer MoS₂ under visible light irradiation,HAuCl₄ without any other chemical reagents.The reduction can be ascribed to the single layer of MoS₂ with the band gap of 1.86 eV.According to the relationship between the bandgap energy（eV）and the wavelength of the electromagnetic wave λ（nm）,it is possible to obtain that 1.86 eV is equivalent to 700 nm,which locates at the near-infrared spectral region.Therefore,excitation electrons can be easily produced from MoS₂ under visible light.It is believed that monolayer MoS₂ is suitable to manufacture photoelectric catalytic materials and devices.Through SEM,TEM,XRD and other methods,we systematically characterize the morphology and structure of the synthesized nanomaterials.In order to explore the photocatalytic degradation of methylene blue,MoS₂-AuNPs nanocomposites are studied by UV-Vis spectroscopy,which is much better than that of monolayer molybdenum sulfide（20 min,> 40% vs.140 min.<20%）.The enhancement in photocatalytic efficiencycan be due to the addition of gold nanoparticles to increase the efficiency of photo-excited electrons.3.Cu₂O/TiO₂/graphene composite nanomaterials are successfully prepared for the application of photodegradation of methylene blue（MB）.Here,as for the presence of Cu²⁺ defects in Cu₂O crystal,Cu₂O,as a high-quality p-type semiconductor,possessan excellent band position,good hole-conduction properties and conduction to hole.The morphology,structure and properties of the synthesized nanomaterials are characterized by XRD,FT-IR spectroscopy and UV-Vis spectroscopy.It is found that the photocatalytic degradation rate of TiO₂/graphene on methylene blue（15min,> 90%）is much greater than that of TiO₂/graphene on methylene blue（20min,<40%）,which indicates that Cu₂O plays an important role in the systemas a sensitizer.