Synthesis And Performance Of Nano Core-shell Type CdS-based Composite Photocatalysis

Photocatalysis technology has been considered as a novel“green”approach to great prospect of application in the field of energy and environment.CdS,the typical semiconductor material,becomes the focus of our research due to the response to visible light.However,CdS is prone to photocorrosion in oxygen-containing aqueous media during photocatalytic reaction.And,the construction of core-shell structure nanocomposite provides possibility to solve the corrosion problems of CdS.In addation,strong light trapping properties of the hollow structure material are conducive to the absorption of light in photocatalysis.However,the adsorption of the hollow nanostructure materials on pollutants mainly depends on the adsorption capacity of the electrostatic,hydrogen bonding and weak?bond,and regulating its pore size and surface properties of the surface can increase the adsorption capacity.But there is no core in this core-shell structure and lost the synergistic effect between the inner core and outer shell.Furthermore,the material between the core and shell can achieved advantages complementary,but the active sites on the surface of the core catalyst are easily shielded and lose catalysis because of the shell structure.Catalytic performance of the core-shell structure materials in which there is a void space between the core and the shell is higher than that of the non-voided between core and shell.Thus,design and production of a new hollow interlayer core-shell type photocatalyst with hollow core and a void space between core and shell can significantly improve and expand the application of core-shell structure in essence.In this dissertation,we has synthesized new hollow interlayer core-shell type photocatalyst with hollow core and a void space between core and shell hollow CdS@@GR,by the bottom-up method using the template-guided layer-by layer self-assembly process from inner to outer under the specific liquid environment,with hollow CdS as core material and grapheme?GR?as shell material.The comprehensive performance of graphene is superior and can be adjusted.In particularly,we pay attention on the micromorphology and ingredient,crystalline phase,pore structure,Uv-vis optical absorption properties,and synthesis mechanism of the hollow CdS@@GR and the intermediates in the process of synthesis.Furthermore,we highlight the hollow CdS@@GR and the intermediates that can be used as photocatalyst.The absorption capacity for dye molecule,photocatalytic degradation behavior,reusability and photocatalytic mechanism of samples are presented and discussed.Firstly,Polystyrene?PS?/CdS core-shell structure nanospheres?CSNSs?were synthesized by facile ultrasonic method with polyvinylpyrrolidone?PVP?as surfactant.In order to understand the formation mechanism and interfacial behavior of the core-shell type microscopic particle in depth,reaction parameters such as PVP,the order of adding precursors,the molar ratio of Cd²⁺/S^2-,as well as the reaction time were carefully investigated.The results showed that the as-prepared nanohybrids were typically core-shell structure with 260nm core and the uniform shell with thickness ranging from 10 to 30 nm,and both PVP and the order of adding precursors were the controlling parameters.Under visible light irradiation with low wattage lamp,PS@CdS composite material exhibited good photocatalytic activity and stability.The successful preparation of PS@CdS composite material for the synthesis of hollow CdS and single core double shell or single core multi-layer core-shell materials provides maneuverability and broaden the potential research value of the CdS-based core-shell structure materials.Secondly,hollow CdS spheres were easily obtained by removing the PS core in toluene solution and calcination.The influence of two different template removal methods on the micromorphology,crystal structure and photocatalytic activity of hollow CdS nanospheres were carefully performed by a comparative study.Results found that the hollow CdS-D had pure cubic sphalerite structure,higher–OH content,less defects and exhibited good photocatalytic activity for Rhodamine-B?RhB?,Methylene Blue?MB?,Methyl Orange?MO?,MB and MO under UV-vis light irradiation with low wattage lamp.However,hollow CdS-C with a hexagonal crystal structure,less–OH content,more defects,have shown poor photocatalytic activity.This indicated that the different template removal methods exhibited a significant influence on the surface micromorphology,crystal structure and photocatalytic activity of hollow CdS nanospheres.Then,the surface of PS@CdS nanoparticles were coated with a layer of SiO₂ using sol-gel process of st?ber method.As a result,PS@CdS@SiO₂ single core double shell structure nanospheres were prepared.Hollow CdS@SiO₂ nanospheres were obtained after removing the PS template by dissolving in toluene solution.Under UV-vis light irradiation with 125 W mercury lamp,the photocatalytic activity of as-prepared PS@CdS@SiO₂ and hollow CdS@SiO₂ sample reduced,but the photocatalytic stability enhanced due to SiO₂layer.Finally,the hollow interlayer core-shell type CdS/graphene composite photocatalysis?hollow CdS@@GR?were synthesized by coassembly between the positively charged amine-modified hollow CdS@SiO₂ and the negatively charged GO,after the reduction of GO with hydrazine hydrate and the removal of SiO₂ layer using HF.The hollow CdS@@GR composite photocatalyst exhibited the strong enrichment ability of pollutant,good photocatalytic activity and repeat performance,which was expected to achieve fast,efficient,green and in situ removal of soluble pollutants with low concentration in the process of water body restoration.