Sythesis And Photocatalytic Hydrogen Evolution Activity Of MoS₂/CdS Hybrid

In recent years,the global demand for energy has increased dramatically,so it is urgent to find a kind of clean and renewable energy.Since TiO₂ electrode for hydrogen production was reported in 1972,hydrogen has attracted much attention as a clean energy with high energy density.New semiconductor materials are developed because of its high photocatalytic hydrogen production performance and provide a new way to solve the energy problem.However,most of the semiconductor photocatalysts have a common defect.The photoexcited electrons and holes are so easy to recombine to reduce the photocatalytic activity.In this thesis,we introduced MoS₂,a member of two-dimensional transition metal dichalcogenieds?TMDs?as a cocatalyst of semiconductor material CdS.By investigating the influences of the different phases of the MoS₂ on the catalytic performances of the composites,we expected to overcome the shortcomings of the CdS photocatalyst.The main results of this thesis are as follows:?1?First of all,the 1T–MoS₂ was exfoliated by the lithium intercalation with assistance of ultrasonication,and the CdS nanorods?CdS NRs?were prepared by hydrothermal method.The 1T–MoS₂/CdS NRs hybrid was synthesized by ultrasonication with the help of surfactant.The morphology of as-prepared samples were characterized by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and X-ray diffraction?XRD?.The phase of 1T–MoS₂ was determinated by Raman spectroscopy?Raman?and X-ray photoelectron spectroscopy?XPS?test.It was found that the photocatalytic hydrogen production rate reached as high as 794.93?mol/h when the weight ratio of 1T–MoS₂ and CdS NRs was 1:10.Besides,the photocatalytic activity of the hybrid was 35 times than pure CdS NRs and the photocatalyst possessed a good stability.?2?To probe the influences of different phase of MoS₂ on the catalytic performances of the hybrid,the 1T–MoS₂ was transformed into 2H–MoS₂ by heating the 1T–MoS₂ in the organic solvent.The 2H–MoS₂/CdS NRs hybrid was then synthesized under the same conditions and same weight ratio as the 1T phase counterpart.The morphology and phase of hybrid were studied by means of SEM,TEM,XRD,Raman and XPS.The 2H–MoS₂/CdS NRs hybrid showed enhanced activity?175.82?mol/h?as expected and only reached 20%of its 1T phase counterpart.To study the mechanism of the photocatalytic reaction,UV-vis and electrochemical impedance spectroscopy?EIS?were also employed.It is founded that the excellent performance of 1T–MoS₂/CdS NRs hybrid should be ascribed to the ohmic contact with low resistance between 1T–MoS₂ and CdS NRs,which differ from p/n junction in the 2H–MoS₂/CdS NRs hybrid.?3?Finally,the amorphous MoS₂ was also synthesized by hydrothermal method with the addition of surfactant,in order to study the influence of the morphologies.The morphology and elemental composition of the samples were characterized by SEM,TEM,XRD and XPS.It was suggested that the amorphous MoS₂ alone was not a good electrode material for hydrogen electrolysis.