The Synthesis And Photoactivity Evaluation Of MoS₂-based Composite Photocatalyst

The catalytic degradation of organic pollutants by using semiconductor material as a photocatalyst has the advantages of simple reaction conditions,high efficiency,non-toxicity,etc.,and has shown its unique efficacy in energy and green chemistry.Now it has become a research hotspot in the field of sewage treatment technology.As an important non-precious metal promoter,molybdenum disulfide has a narrow band gap,strong visible light absorption,good chemical stability,and great potential in the field of environmental pollution control and energy.Based on the modified theory of photocatalytic materials,MoS₂/g-C₃N₄ and MoS₂/Bi₂S₃ composite photocatalysts with heterostructures were prepared in this dissertation.The as-prepared samples were characterized by XRD,SEM,TEM,BET,UV-Vis,XPS and other technologies,and the methylene blue was used as the simulated pollutant to investigate the photocatalytic activity and stability.The relationship between the heterostructure and photocatalytic reaction mechanism was also discussed.In this paper,MoS₂ monomer photocatalyst was synthesized by hydrothermal method,using sodium molybdate as molybdenum source and thiourea as sulfur source.Molybdenum disulfide nanosheets assembled into flower globular,with good crystallinity and larger specific surface area,but also has responses in the visible range of light.MoS₂ prepared under the experimental conditions of when hydrothermal temperature is 210°C,and the ratio of sodium molybdate to thiourea is 1:5,the as-prepared MoS₂ has the best photocatalytic activity with good stability.When the dosage of photocatalyst is 0.5 g·L^-1 and the initial concentration of methylene blue is 10 mg·L^-1,1:5 MoS₂ can exhibit high photocatalytic activity.In this thesis,MoS₂/g-C₃N₄ were prepared by ultrasonic-assisted method to prepare photocatalyst.The results showed that the MoS₂ nanospheres were ultrasonically stripped to MoS₂ nanosheets and successfully loaded on the surface of g-C₃N₄ material,increasing the active sites of the material.the heterostructure was formed that made the photoluminescence intensity of the material obvious Reduce and inhibit recombination of photogenerated electron-hole pairs,and improve the utilization efficiency of carriers.The photocatalytic activity of the prepared composite photocatalyst was higher than that of g-C₃N₄ monomer.When the loading amount of MoS₂ was 3 wt.%,the photocatalytic activity was the best,reached 82.1%after 180min,and showed good Stability.it was found that 3 wt.%MoS₂/g-C₃N₄ exhibited the highest photocatalytic degradation efficiency which was 95.7%,but also has a good a good stability.MoS₂/Bi₂S₃ heterojunction photocatalyst was synthesized by simple one-step hydrothermal method,using bismuth nitrate pentahydrate as bismuth source,sodium molybdate as molybdenum source and thiourea as sulfur source.The results show that MoS₂ grows in the form of nanosheets on the surface of Bi₂S₃ micro-rods.The two are in full contact with each other to form heterostructures,which increased the specific surface area and active sites of the material,and promoted the separation of photo-generated carriers,and inhibited recombination of photogenerated electron-hole pairs.The photocatalytic activity of composite materials compared to two monomers has a great improve.When the mass ratio of sodium molybdate to lanthanum nitrate pentahydrate is 1:2,the prepared BM-2 heterojunction catalyst has the best catalytic performance,and the degradation rate of methylene blue reaches 96.4%after 180 min of visible light irradiation and shows a good universality and stability.