Preparation Of Cadmium Sulfide And MOF Based Materials And Their Photocatalytic Performance Study

The large-scale use of fossil and some other non-renewable resources has brought about a global energy crisis and environmental problems.The search for clean and sustainable alternative energy sources has been an urgent need for the rapid development of society,and it has attracted a lot of attention from researchers.Therefore,how to effectively develop and utilize renewable energy sources such as solar energy is very promising in solving energy shortage.Among them,the application of photocatalysis in the fields of hydrogen production by water splitting and carbon dioxide reduction has been considered as an initiative to solve environmental problems.However,in most cases,the half-reactions containing toxic and expensive sacrificial agents are the main ones.Owing to the slow kinetics of the half-reactions,the overall photocatalytic process is inhibited,which intensifies the cost of photocatalysis.In addition,semiconductors and metal-organic frameworks（MOFs）materials have been widely used in various fields such as photocatalysis due to their excellent properties.Based on the above points,we chose Cd S-based composites（Cd S@Mo S₂,Cd S/MIL-53（Fe））for the coupling reaction of photocatalytic hydrogen production and selective oxidation of benzyl alcohol.Since the film can solve the defects of light scattering,easy agglomeration and poor recyclability,we have also successfully prepared a zirconium-based metal-organic framework film and applied it to the photocatalytic overall carbon dioxide reduction.The specific work is as follows:1.Construction of a heterojunction catalyst,Cd S@Mo S₂,for visible-light-driven efficient hydrogen production coupled with selective oxidation of benzyl alcohol,and two high value-added products were obtained simultaneously.Among them,the hydrogen yield of Cd S@Mo S₂ was much higher than that of Cd S nanorods,and the selectivity of oxidation product benzaldehyde reached 99%.The formation of a p-n heterojunction between Cd S and Mo S₂ was demonstrated by scanning electron microscopy（SEM）and transmission electron microscopy（TEM）image characterization.In addition,we proposed the mechanism of photogenerated charge transfer and separation,which was verified by electrochemical characterization.The results show that the Cd S@Mo S₂heterostructure adopts a Z-scheme charge transfer mechanism,which improves the charge separation and transfer efficiency,resulting in a great enhancement of photocatalytic activity2.Cd S decorated metal-organic framework composites（Cd S/MIL-53（Fe））were successfully synthesized and used in the reaction of hydrogen production coupled with benzyl alcohol oxidation.It was found that the excellent hydrogen-producing activity and high selectivity for benzaldehyde were exhibited under visible light irradiation,which far exceeded that of the single MOF and Cd S.Photoluminescence（PL）,photocurrent and electrochemical impedance spectroscopy（EIS）showed that the Cd S/MOF composites have faster charge transfer as well as inhibition of photogenerated charge recombination,ultimately improving the photocatalytic activity.Also,the reaction mechanism of Cd S/MOF composites in photocatalytic coupling is proposed using Mott-Schottky characterization as well as analysis.3.PET@NH₂-Ui O-66 film was successfully prepared with PET fiber as the substrate by a simple hydrothermal method,and the visible-light-driven photocatalytic overall CO₂reduction was investigated in pure water system over MOF film.The application of MOF powder in photocatalysis is limited by the disadvantages of easy agglomeration,light scattering and poor recyclability,while the photocatalysis of MOF film can be a good solution to this defect.The photocatalytic results show that PET@NH₂-Ui O-66 film has excellent photocatalytic activity,and its reusability is better than that of NH₂-Ui O-66powder.