The Preparation And Photocatalytic Activity Research Of Tungstate-based Nano-materials

Utilization of solar energy triggering a series of photocatalytic reaction,such as water splitting,CO₂ reduction and pollution mineralization,can help to solve some problems including energy shortage and environmental pollution.However,the photocatalytic activities of traditional photocatalysts like Ti O₂ and Zn O are restricted due to some severe drawbacks,such as limited light absorption,rapid recombination rate and lower migration efficiency of the charge carriers.This work focuses on synthesing and modifying the tungstate semiconductors including Mn WO₄ and Bi₂WO₆,in which Mo S₂/Mn WO₄,Mn WO₄/g-C₃N₄ and Ag/WO₃/Bi₂WO₃ nanocomposites are prepared.A series of characterization were used to investigate the composition,morphology,structure,optical and electrical properties of the prepared samples.The photocatalytic performances of the prepared samples were measured by using different photocatalytic reaction.Combined with the results of characterizations and photocatalytic activities,the structure-activity relationship of the prepared samples can be studied.The specific research contents are showed in follows:?1?The amorphous Mo S₂ and pure Mn WO₄ are synthesized successfully by solvothermal and hydrothermal method,respectively.The Z-scheme Mo S₂/Mn WO₄composite is constituted by a facile solvothermal approach.The characterization results show that the introduction of Mo S₂ facilities to enhance the light absorption of Mn WO₄due to the narrow band gap of Mo S₂.Besides,the p-n heterojunction between Mo S₂ and Mn WO₄ can efficiently improve the migration rate of the photo-generated charge carriers.The results of photocatalytic O₂ evolution reveal that the 0.5%Mo S₂/Mn WO₄composite achieves the best photocatalytic activity of 223?mol/g in 3h,which is 1.2 and 2.6 times higher than that of bare Mn WO₄ and Mo S₂,respectively.?2?A Mn WO₄/g-C₃N₄ heterojunction was synthesized by hydrothermal method for photocatalytic H₂ generation.The characterization results show that the constitution of Mn WO₄/g-C₃N₄can not only improve the ability of light absorption of g-C₃N₄ but also enhance the separation efficiency of photo-generated charge carriers.In addition,the Mn WO₄/g-C₃N₄ nano-composite has higher specific area than the bulk g-C₃N₄.Because of the suitable band structure between Mn WO₄ and g-C₃N₄,the Mn WO₄/g-C₃N₄composite possesses enhanced H₂ evolution rate and the 5%Mn WO₄/g-C₃N₄ achieves the highest H₂ yield of 2820?mol/g in 3h,which is 3.8 times higher than that of bulk g-C₃N₄.In addition,the H₂yield can be raised to 5033.9?mol/g when the p H value of photocatalytic system is adjusted to 14.?3?A WO₃/Bi₂WO₆ nanoflower was synthesized by a facile hydrothermal method and Ag nanoparticles was loaded on the surface of WO₃/Bi₂WO₆by a photo-deposition approach.The Ag/WO₃/Bi₂WO₆ has superior optical properties than pure Bi₂WO₆,WO₃and WO₃/Bi₂WO₆heterojunction due to the surface plasmon resonance?SPR?effect.In addition,the constitution of Z-scheme heterojunction between Bi₂WO₆ and WO₃ can enhance the migration and separation efficiency of charge carriers so that the composites have better photocatalytic activity for chlorobenzene degradation.The results of the degradation experiment reveal that the 2%Ag/WO₃/Bi₂WO₆is the optimum composite and can degrade 80%of chlorobenzene during 10h,which is 1.8 and 2.8 times higher than that of pure Bi₂WO₆ and WO₃/Bi₂WO₆ composite.