Synthesis Of Photocatalysts Based On CdS And Their Performance Studies On Selective Oxidation Of Benzyl Alcohol

Selective oxidation of aromatic alcohols to the corresponding carbonyl compounds is a fundamental but significant reaction in organic synthesis.The carbonyl compounds such as aldehyde and ketone derivatives are widely utilized in the fragrance,confectionary and pharmaceutical industries since they are one of the important chemical materials.Among them,the selective oxidation of benzyl alcohol to benzaldehyde has attracted the most attention because it has the most widely applications.However,traditional oxidation generally depends on a great deal of oxidants,such as chromate,permanganate,which not only released corrosive gas and related organic waste,but also difficult to separate the products.Therefore,enormous attention has been devoted to exploiting a clean and environmental-friendly approach to replace the traditional production mode for organic synthesis.As a branch of green chemistry,photocatalysis is just the alternative for the conventional oxidation since the mild experiment condition,the green,environmental-friendly concept.Drive the oxidation reaction just through semiconductor photocatalysts which utilize solar energy and O₂ in nature.Therefore,the study on the applications of photocatalysis technology for selective oxidation of benzyl alcohol to benzaldehyde has been a hotspot already.The point of photocatalytic technologyis to select or prepare a suitable photocatalysts.Recently,numerous semiconductor photocatalysts have been investigated,such as TiO₂,ZnO,ZnS,CdS,CuS and BiVO₄.CdS has been extensively studied due to its suitable band gap?2.4 eV?.We prepared CdS and its composite material,and the photocatalytic performance of samples has been studied in this thesis.The main contents and results as follows:?1?The cubic and hexagonal phase CdS nanoparticle was synthesized by microwave reduction-vulcanizing method.The structure,textural,and optical properties of the samples were characterized by several techniques,such as XRD,SEM,TEM,and UV-Vis DRS.The photocatalytic performance of the as-synthesized CdS nanocomposites were evaluated by selective oxidation of benzyl alcohol to benzaldehyde under visible light irradiation.Under illumination for 2 h,the conversion of benzyl alcohol and the selectivity of benzaldehyde are about 84%and 96%,respectively.?2?Introduce reduced graphene oxide?rGO?on basis of the research content?1?,a series of rGO/CdS nanocomposites with different weight ratios of r GO have been synthesized via afacile microwave reduction-vulcanizing method.XRD,UV-Vis DRS,SEM,TEM,PL and EIS areemployed to determine the stucture and morphologyof the samples.It was found that the CdS nanoparticles are distributing on the reduced graphene oxide scaffold uniformly.And the properties of rGO/CdS nanocomposites,including morphology,optical,and electronic nature,are able to be tuned by the addition of rGO as compared with pure CdS prepared in the absence of rGO.The photocatalytic properties of the as-prepared rGO/CdS nanocomposites are evaluated by selective oxidation of benzyl alcohols under a mild condition.Our results demonstrate that the as-prepared rGO/CdS nanocomposites can serve as a promising visible-light-driven photocatalyst for the selective oxidation of alcohols to corresponding aldehydes.The high photoactivity of rGO/CdS can be ascribed to the integrative effect of high electron conductivity of rGO,and its significant influence on the morphology and structure of the samples.The optimum percentage of rGO is 10 wt%.Under illumination for 1 h,the conversion of benzyl alcohol and the selectivity of benzaldehyde are about 82%and 97%,respectively.?3?The g-C₃N₄/CdS photocatalyst was prepared via precipitation method.The photocatalyst was characterized by XRD,SEM,TEM and UV-Vis DRS.Compared with single g-C₃N₄ and CdS,the g-C₃N₄/CdS photocatalyst exhibits the best photocatalytic activity under visible light illumination.The synergic effect ofg-C₃N₄ and CdS,which can effectively separate and transfer photoexcited carriers,was proposed to be responsible for the enhancement of the photocatalytic activity.The optimal proportion of g-C₃N₄ is about 10 wt%.Illuminated for 1 h,the conversion of benzyl alcohol and the selectivity of benzaldehyde are about 84%and 96%,respectively.