Construction Of CdS-based Nanocomposite And Research On The Mechanism Of Photocatalytic Water Splitting To Produce Hydrogen

Using semiconductor nanomaterials as photocatalysts for photocatalytic hydrogen production is one of the ideal ways to realize solar-driven chemical reactions.Cadmium sulfide(CdS)semiconductor has excellent light response characteristics in the visible wavelength range,and has an energy band structure that matches water splitting.It is a high potential photocatalytic material.However,the formed photo-generated electron-hole pairs are prone to recombination inside the cadmium sulfide material and the photo-generated holes can easily lead to serious photo-corrosion phenomena.These shortcomings affect its application in photocatalysis.Therefore,continuous exploration is needed to improve the photocatalytic activity and stability of sulfides.In view of the current problems of cadmium sulfide,this thesis designs and constructs a series of cadmium sulfide nanocomposites from the structure to promote the spatial separation of photo-generated charges,thereby effectively inhibiting photo-generated carrier recombination and photo-corrosion,so as to improve photocatalytic hydrogen production The purpose of efficiency.The specific research content is as follows:(1)Firstly,one-dimensional CdS nanorods were synthesized by solvothermal method,and then a layered 1T phase MoSe₂nanomaterial with a stable structure was loaded on the surface of the prepared CdS nanorods.Adjust the doping amount of MoSe₂nanosheets and compare the photocatalytic hydrogen production activity.It is found that the best doping amount of MoSe₂is10 wt.%of the composite material(CM-10),and the hydrogen production rate can reach 25.8mmol·g^-1·h^-1,which is 4.2 times that of CdS nanorods.The morphology,structure and chemical properties of the synthesized CdS/1T-MoSe₂nanocomposite were studied through phase,composition,morphology and photoelectrochemical performance analysis.The reason for improving the hydrogen production performance of the composite material is that the doped MoSe₂nanosheets act as a transmission medium and strengthen the light absorption of the composite material,so that the photogenerated carriers are quickly separated and transported at the interface of CdS and MoSe₂.In addition,the electron spin resonance spectroscopy test is used to further explore and clarify the mechanism of the photocatalytic reaction.(2)CdS nanorods and 1T-WS₂flower-like nanosheets were synthesized by solvothermal method.CdS nanorods were used as matrix materials,and WS₂nanosheets and CdS nanorods were mixed and loaded through a simple hydroalcohol system.Adjust the loading capacity of WS₂nanosheets,and study the hydrogen production activity of CdS/WS₂composites under different loading ratios.Experiments have found that when the loading ratio is 10 wt.%,the hydrogen production rate of the CdS/WS₂composite can reach 69.5 mmol·g^-1·h^-1,which is about11.6 times that of pure CdS.The morphology,structure and chemical properties of the synthesized CdS/WS₂composite were studied in detail through phase,composition,morphology and photo-electrochemical performance analysis.It is found that the improvement of the hydrogen production performance of the composite material is due to the excellent metal conductivity and larger specific surface area of the loaded 1T-WS₂nanosheets,which are more closely loaded with the CdS nanorods.So that the photogenerated carriers in the composite material can be separated and transported faster.On this basis,the mechanism of enhancing the photocatalytic activity of CdS/WS₂composites was further studied.(3)Further innovative synthesis of CdS/WS₂composite materials,a two-step solvothermal method was used to synthesize 1T-WS₂/CdS photocatalytic heterojunction material in situ.The solvothermal method was used to first synthesize CdS nanorods as the matrix material,and on this basis,direct in-situ synthesis of loaded WS₂nanosheets to obtain 1T-WS₂/CdS heterojunction photocatalyst.By adjusting the amount of CdS nanorods,the hydrogen production activity of heterojunction materials under different loading ratios was studied,and it was found that when the loading ratio was 5 wt.%,the hydrogen production rate reaches 31.5 mmol·g^-1·h^-1,which is6.2 times that of pure CdS.Through the research and analysis of the phase,composition,morphology and photoelectrochemical performance of the heterojunction material,it is found that the improvement of the hydrogen production performance of the composite material is due to the formation of a tight heterogeneity between the in-situ synthesized 1T-WS₂nanosheets and the CdS nanorods.In the heterosjunction structure,due to the excellent metal conductivity of1T-WS₂,the photo-generated carriers generated in the photocatalytic reaction can be quickly separated and transferred at the interface and between the materials.