Preparation Of Cadmium Sulfide-based Photocatalysts And Their Application In Heterogeneous Photocatalytic Oxidation Reactions

With the continuous development and progress of society,the country pays more and more attention to the utilization and development of clean energy.Traditional production methods of organic products consume high energy and have heavy pollution,and it is urgent to develop clean and pollution-free organic reaction pathways.The selective oxidation of photocatalytic organic matter uses solar energy as an energy source,which makes the oxidation process green and clean.More importantly,the oxidation products of the photooxidation process have high selectivity,which attracts many scientific researchers to conduct in-depth research.The core of many photocatalytic selective oxidation reactions is the design of high-efficiency photocatalysts.In this paper,cadmium sulfide with different morphologies and CdS-based composite materials were prepared by solvothermal and chemical bath deposition methods,and applied to photocatalytic oxidation reactions.The reaction mechanism was deeply explored.The main research contents are as follows:Research on CdS nanomaterials with different morphology.CdS nanoparticles were prepared using Cd（CH₃COO）₂·2H₂O and thioacetamide as raw materials;CdS nanosheets were prepared using cadmium chloride and thiourea as raw materials,ammonia water and sodium citrate as surfactants;Using cadmium chloride and thiourea as raw materials and Si O₂ spheres as templates,CdS nanospheres were prepared;Using cadmium chloride and thioacetamide as raw materials,hexamethylenetetramine and polyvinylpyrrolidone as surfactants,ethylenediamine as solvent,CdS nanorods were prepared by solvothermal method.Four different morphologies of CdS are used in the photocatalytic oxidative coupling reaction of benzylamine.Among them,CdS nanorods have the best catalytic effect.The conversion rate of benzylamine can reach 81%,and the CdS nanospheres can reach 50%.Photocurrent and electrochemical impedance tests show that CdS nanorods have stronger photo-generated electron-hole separation ability.The electron spin resonance（ESR）test shows that CdS nanorods have a stronger ability to generate ¹O₂ than nanoparticles.Cyclic testing shows that the high catalytic performance of CdS nanorods is closely related to their high crystallinity.Research on UiO-66 loaded CdS material（CdS/UiO-66）.Using ZrCl₄ and terephthalic acid as raw materials,glacial acetic acid as surfactant,and N,N-dimethylformamide（DMF）as solvent,UiO-66 was prepared by solvothermal method.Using Cd（CH₃COO）₂·2H₂O and thioacetamide as raw materials,CdS nanoparticles with different contents were loaded on the surface of UiO-66 by chemical bath deposition to prepare CdS/UiO-66-X composite materials.It is applied to the photocatalytic oxidative coupling reaction of benzylamine.Among them,CdS/UiO-66-3 has the best catalytic effect,and the conversion rate of benzylamine is 66%.Quenching experiments show that the main active species in the reaction are holes and ¹O₂.The photocurrent results prove that CdS/UiO-66-3 has a stronger ability to transmit photogenerated carriers than UiO-66.The ESR test shows that CdS/UiO-66-3 can convert O₂ molecules into¹O₂ molecules more efficiently.Research on CeO₂ Supported CdS material（CdS/CeO₂）.Using cerium（Ⅲ）nitrate hexahydrate as raw material,sodium hydroxide as precipitant,and urea as surfactant,CeO₂nanoparticles were prepared by hydrothermal method.Using Cd（CH₃COO）₂·2H₂O and thioacetamide as raw materials,CdS nanoparticles and CeO₂ are combined by chemical bath deposition to form a semiconductor heterojunction CdS/CeO₂.When applied to the photocatalytic selective oxidation of benzyl alcohol to prepare benzaldehyde,using air as the oxidant and benzotrifluoride as the solvent,the conversion rate of benzyl alcohol is 94%,which is 13 times that of CdS nanoparticles,and the selectivity of benzaldehyde is as high as 98%.The quenching experiment proved that the main active species of the reaction is superoxide anion（·O₂-）.The ESR test shows that CdS/CeO₂ can efficiently convert O₂ molecules into·O₂-molecules.The cycle test shows that the composite material CdS/CeO₂ has good cycle stability.The photo-corrosion phenomenon of CdS has been suppressed to a certain extent.