Synthesis And Characterization Of Nanosized Bismuth Complex Oxides As Photocatalysts

Environmental pollution and the shortage of energy sources are the most serious problems among recent environmental issues in the world. Many investigations have been focused on how to solve the two problems. Titania as an oxide semiconductor photocatalyst appears to take on a promising and important prospect in environmental purification due to its strong oxidizing power, photoinduced hydrophilicity, nontoxicity and long-term photostability. However, its large band gap and fast recombination rate of photogenerated electron/hole pairs hinder the commercialization of this technology in a certain extent. Recently, many compounds contained Bi ion have been well known as new photocatalysts, which could be used in a visible light region, such as Bi₂InNbO₇,Bi₄Ti₃O₁₂,Bi₂Ti₂O₇,Bi₁₂TiO₂₀,Bi₂WO₆ and BiVO₄. Nevertheless, there are still such inherent limitations as reduced photocatalysts'activity due to high synthesizing temperature and other shortcomings in the preparation process of photocatalysts. Therefore, this thesis, based on new ideas in synthesizing process, mainly focuses on the following research works to prepare highly active photocatalytic materials contained Bi ion:1. Bi₁₂TiO₂₀ regular tetrahedron single crystals were successfully synthesized by a simple hydrothermal process for the first time with using Ti(OC₄H₉)₄ and Bi(NO₃)₃·5H₂O as raw materials, KOH as mineralizers and by adjusting the KOH concentration, reaction time and temperature. The powders obtained are of good quality such as high purity, high degree of crystallinity and well-controlled morphology. Their average particle size is about 10μm. The optimal processing condition: [KOH]=4.5M, reaction temperature is 180℃and reaction time 4h.Nearly spherical Bi₁₂TiO₂₀ nanocrystals were synthesized at 140oC for 1h via a novel isopropanol–assisted hydrothermal method with using Bi(NO₃)₃·5H₂O and Ti(SO₄)₂ as reactants and introducing 20vol% of isopropanol. The resultant powders with a good crystallinity were about 10 nm in size. Their UV-Vis absorption spectra revealed that the...