Nanostructure Semiconductor Photocatalyst Synthesis And Characterization Of Bi-mo (m = W, Fe) Liquid

In recent years, environmental and energy problems have attracted much attention. Photocatalyst could decompose almost all the organic and inorganic pollution into small inorganic molecules and achieve to purify the environment. It would be a great advance if the photocatalyst could get wider wavelength response range, higher energy transformation rate and stability.TiO2 has been the most widely used semiconductor in the photocatalytic field. However, because of its wide band gap (3.2 eV), there are many limitations in the application. Many methods were exploited to extend the responding wavelength range of the catalyst, like doping TiO2 with other elements and developing novel narrow band gap semiconductor catalysts. This thesis reported two complex oxides of Bi with narrower band gap and the main contents were concluded as follows:1. Bi2WO6 nanopowders have been synthesized by a facile hydrothermal method using ethylene glycol as the solvent. With the aid of sodium dodecylbenzene sulfonate as surfactant, different superstructures such as multilayered disks and micro-disks could be attained. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis absorption spectroscopy. The photocatalytic activity was estimated by the degradation of RhB under visible light irradiation. The results show that the single-layered disks are composed of nanoparticles with average diameter less than 10 nm and they have excellent photocatalytic activity. The formation mechanism of the disks and the relationship between the photocatalytic activity and the shape of the microstructures were further studied.2. Try to fabricate Bi2WO6 nanopowders through molten salt synthesis method. In the molten salt system, Bi(NO3)3·5H2O and Na2WO4·2H2O were used as reactant and the mixture NaNO3 and LiNO3 with the molar ratio of 0.463 as solvent. The final product was detected by X-ray diffraction and scanning electron microscopy. It is found that the temperature and the ratio of the molten salt had great effect on the component and the morphology on the product.3. Multiferroic BiFeO3 nanoparticles were prepared by a sol-gel rapid calcination technique. The obtained products were analyzed by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis spectrophotometer. The as-prepared sample calcined at 500℃is pure orthorhombic phase and the average particle size is about 35 nm with narrow size distribution. The band gap was estimated to be only 2.05 eV and it indicates their potential application as visible-light-response photocatalyst. The photocatalytic property of BiFeO3 nanoparticles was estimated by the degradation of Rhodamine B(RhB) under visible light irradiation and the photocatalytic activity under different pH values was further studied for the first time. The result shows that the BiFeO3 nanoparticles have the highest photocatalytic activity in the solution with the lowest pH value.