Composition Control,auxiliaries Modification And Photocatalytic Properties Of Zn_1-xCd_xS Nanoflakes

Photocatalytic decomposition of water as a renewable green hydrogen production process has attracted much attention in recent decades.CdS is widely used in the field of photocatalytic hydrogen production due to its narrow band gap,strong light absorption coefficient and suitable band position among various photocatalytic semiconductors.In order to expand the specific surface area and promote charge transfer,CdS is often made into quantum dots(zero-dimensional),nanorods(one-dimensional),nanosheets(two-dimensional)and nanoparticles(three-dimensional)and other nanostructures.Compared with the zero-dimensional and three-dimensional nanostructures,one-dimensional and two-dimensional CdS have less carrier recombination and faster charge transfer,so they exhibit excellent photocatalytic performance.Among them,CdS nanoflakes can not only provide a good substrate for the growth of the catalyst,but also help to control the interface properties of the heterojunction to achieve effective charge separation.However,due to the poor photochemical stability of CdS itself,it is often necessary to modify the co-catalyst to suppress the photocorrosion.Although the catalytic performance of precious metal co-catalyst is better,the cost is higher.Therefore,it is critical to explore the non-precious metal and abundant co-catalyst and its composite with CdS to improve the performance of photohydrolytic water for hydrogen production.In this paper,Ni(OH)₂/CdS,Zn CdS/Zn S(En)_0.5(ZCS-ZSEn for short)composite nanosheets were constructed to improve the light absorption efficiency,accelerate charge separation and transfer,combined with their higher specific surface area to provide active site density for hydrogen evolution catalytic reaction,and then achieve higher solar hydrogen production efficiency.Specific research contents are as follows:Firstly,a photoassisted deposition method was proposed to modify Ni(OH)₂nanoparticles on the flowers synthesized by hydrothermal method of CdS nanosheets.The plane size and thickness of the Ni(OH)₂/CdS composite nanosheets are 1.5 um and 20 nm,respectively,and the particle size of Ni(OH)₂is about 5 nm.By controlling the photodeposition time,the load of Ni(OH)₂particles can be adjusted,and then the light absorption,interfacial electrical transport and photohydrolytic properties of the composite nanosheets can be regulated.The longer the photodeposition time is,the higher the loading density of Ni(OH)₂particles is,and the photocatalytic hydrogen production performance of the composite samples increases at first and then decreases.Mechanism analysis showed that Ni²⁺doped by extending the range of visible light absorption composite nanometer piece,CdS and Ni(OH)₂between"?"type of band structure effectively promoted the charge separation and transfer,combined with the specific surface area of the composite structure provides its ehrs with plenty of active site,finally led to the best production rate of hydrogen(20.14mmol/g/h),is about pure CdS nanoparticles produced three times the rate of hydrogen.Furthermore,ZCS/ZSEn composite nanosheets were prepared by one-step hydrothermal method,and the morphology,composition,crystallization properties and photolysis properties of the nanosheets were studied.Compared to CdS,ZCS/ZSEn composite nano patches of light absorption for enhanced obviously,the charge transfer resistance fell to 8043 from14860?.The photocatalytic hydrogen production rate of 139.02 mmol/g/h was achieved,which was about 80 times that of pure CdS nanosheets and 31 times that of Zn S(EN)_0.5nanosheets.In conclusion,through the construction,structure and composition regulation of Ni(OH)₂/CdS and ZCS/ZSEn composite nanosheets,the photocatalytic hydrogen production efficiency has been greatly improved.Combined with the mechanism analysis,it provides a certain material basis and theoretical basis for the further research and development of high efficiency photocatalyst.