Visible Light Response Photocatalysts Bismuth Tungstate（Bi₂WO₆） Modified Study

As a kind of visible light driven photocatalyst, Bi2WO6displays potential photocatalytic efficiency to many contaminants under visible light. One of the effective ways to improve the photocatalytic efficiency of Bi2WO6is to modify it with other materials. Boron doped Bi2WO6and magnetic Bi2WO6/Fe3O4composites were synthesized and a higher photocatalytic efficiency was achieved. Two major parts were included in my thesis:(1) Bi2WO6doped with different amounts of boron atoms (0.1,0.5,1.0,5.0and10%B) were synthesized using hydrothermal method and their photocatalytic activities to degrade rhodamine B (RhB) under simulated solar light was investigated. The successful incorporation of B atoms in Bi2WO6was proved by IR, Raman spectra and XPS. Doping with B could affect the pore structure and volume.0.5%displayed more mesopores with higher total pore volume than pure6; while the pores of10%B/Bi2WO6mainly distributed in microporous range with much less total pore volume. As a result,0.5%B/Bi2WO6displayed stronger adsorption capacity to RhB, favoring the photodegradation. In addition, the doped B atoms could act as electron traps and facilitate the separation of photogenerated electron-hole pairs due to its electron deficient and oxytropic characteristics.0.5%B/Bi2WO6displayed the highest photocatalytic activity under simulated solar light with rate constant (kobs)8.8times of that using pure Bi2WO6. Its photoactivity was affected by solution pH and the optimum was achieved at pH7. At this condition, around100%of RhB (10-5mol/L) was degraded in180min. The photogenerated holes were the main active species responsible for the photodegradation of RhB by B/Bi2WO6.(2) Composite Bi2WO6and Fe3O4photocatalysts were synthesized using hydrothermal method and their photocatalytic activity to degrade rhodamine B (RhB) under visible light irradiation assisted by H2O2was investigated. The successful incorporation of Fe3O4in Bi2WO6was proved by XRD, IR, and DRS. The composite photocatalysts could be easily harvested from the reaction solution by an external magnetic field due to the magnetic property. In the presence of H2O2, a large amount of·OH radicals were produced by reacting with photogenerated electrons. Fe3O4could promote the separation of hole-electron pairs and acted as a Fenton-like reagent, expediting the production of·OH radicals. Thus, the composites displayed much higher photocatalytic efficiency to degrade RhB than pure Bi2WO6in the presence of H2O2.95%of RhB (initial concentration10mg/L) was removed in120min irradiation and60%of TOC was removed in180min by0.5g/L Bi2WO6/Fe3O4(5:1). The composite displayed high photodegradation efficiency at pH3-9, while the photocatalytic efficiency decreased significantly at pH11due to the inhibited production of·OH radicals.