Preparation And Properties Of Bi₂WO₆ Composite Powders And Thin Films

In recent years,environmental problems have become serious increasingly,so people seek green,safe and effective ways to solve the problem of environmental pollution,especially the treatment of organic dyes in industrial wastewater.Due to its unique morphology,excellent properties and wide range of applications,nano semiconductor materials have been used in photocatalytic degradation,photocatalytic hydrogen production and adsorption degradation.Bi₂WO₆ nanomaterials have attracted extensive attention in the fields of adsorption and photocatalysis due to its unique laminar structure.But pure Bi₂WO₆ always have some disadvantages such as low specific surface area,large band gap and short carrier life.In this paper,Bi₂WO₆/BiOCl composite adsorbent with hierarchical structure was firstly synthesized.The adsorption performance and mechanism were studied.Then,Bi₂WO₆ films and Bi₂WO₆/WO₃ composite films were synthesized and their photochemical properties and potential photocatalytic properties were studied.The main content of the paper is as follows:1.Bi₂WO₆/BiOCl composites were prepared by simple one-step hydrothermal method introduced NaCl into Bi₂WO₆ precursors.The structure samples were characterized by X-ray diffraction?XRD?,field emission scanning electron microscope?FE-SEM?and N₂ adsorption-desorption tester?BET?.The adsorption performance of Bi₂WO₆/BiOCl composite material was tested by using organic dyes as adsorption objects.The results showed that Bi₂WO₆/BiOCl composite showed excellent adsorption performance for cationic dyes,especially for methylene blue?MB?dyes.Under normal temperature and pressure,the saturated adsorption capacity of Bi₂WO₆/BiOCl for MB dyes can reach 56.70 mg.g^-1,which is better than most adsorbents.In addition,the adsorption behavior of Bi₂WO₆/BiOCl for MB dyes conforms to the Pseudo-second-order kinetic model and Langmuir isotherm model.Thermodynamic results show that Bi₂WO₆/BiOCl is more favorable for the adsorption of MB dyes at low temperature,and the adsorption process is mainly physical adsorption,which is consistent with the infrared analysis results.2.Bi₂WO₆ film and Bi₂WO₆/WO₃ composite film were successfully synthesized by electrochemical method and immersion method.The crystal structure and microstructure were characterized by XRD,Raman and FE-SEM.Scanning electron microscope was used to observe Bi₂WO₆ thin films,which prepared with different heat treatment conditions.Morphology shows that there are large number of pores on the surface of Bi₂WO₆nanosheet.Andthelowerthetemperature,themoresurfacedefects.he photoelectrochemical properties of Bi₂WO₆ thin films prepared under different conditions were studied by electrochemical workstation.The test results show that Bi₂WO₆ film calcination 6 hours by 520?have the best photoelectrochemical properties.Bi₂WO₆/WO₃composite films were prepared by changing the titration of?NH₄?₂WO₄,and it was found that the photoelectrochemical properties of Bi₂WO₆ films were improved after WO₃compound.The UV-visible diffuse reflectance spectra?DRS?results show that when the titration of?NH₄?₂WO₄ is 50?L.cm^-2,the band gap of the prepared Bi₂WO₆/WO₃composite film is about 2.55 eV,which is lower than 2.70 eV of the pure Bi₂WO₆ film.Meanwhile,after 10 h of visible light irradiation,Bi₂WO₆/WO₃ composite film samples was about 3.5 times as the degradation efficiency of RhB as pure Bi₂WO₆ film.Which indicating that the synergistic effect between Bi₂WO₆ and WO₃ promoted the degradation of RhB dyes.