Study On Synthesis And Photocatalytic Properties Of Visible Light Catalyst Bi₂WO₆

In recent years, photocatalytic technology has received much attention due to its potential application prospect in the fields of using solar energy to solve environmental pollution problem and using light to decompose water into hydrogen. UV-responsive photocatalysts,such as TiO2, have a band gap of about 3.2ev and absorbs only 4% of the Sunlight(UV,?<400nm),which severely limits the use of solar energy. However,the visible light accounts for about 45% of the solar energy, therefore, the visible light response photocatalyst has become a hot spot in the current research. Among them, because of its band gap of about 2.7ev,bismuth tungstate (Bi2WO6) has become a potential visible light responsive photocatalyst.In this paper,bismuth tungsten oxide (Bi2WO6) as visible light catalyst was prepared by a sol-gel method.The samples were characterized by the X-ray diffraction, scanning electron microscope, fourier transform infrared spectroscopy and UV-visible spectrophotometer. The photocatalytic activity of Bi2WO6 was evaluated by photocatalytic degradation of methyl orange under the two different lights. The photocatalytic activity of the two kinds of light sources in the system was examined by simulating the sunlight with ultraviolet light and xenon light respectively. The effects of calcination temperature, pH of methyl orange solution,the initial concentration of methyl orange and the amount of the catalyst on catalyst system were studied. The results indicate that calcination temperature and pH of methyl orange solution were the crucial factors for the photocatalytic activity of Bi2WO6. When Bi2WO6 was calcinated at 400?, it can greatly degrade methyl orange solution at pH=3 the degradation rate of methyl orange approachs 92% in xenon light, while 58% in sun light.By using HNO3 and NH3·H2O to adjust the pH of the reaction,Bi2WO6 powder catalysts with different morphologies and photocatalytic activity were synthesized by template-free hydrothermal method. The as-synthesized Bi2WO6 samples were characterized by X-ray diffraction, transmission electron microscopy, fourier transform infrared spectroscopy, UV-vis diffuse reflectance spectra and N2 adsorption-desorption measurements. When the samples prepared at pH=7, reaction temperature was 180? and reaction time was 24h,the Bi2WO6 samples exhibited optimal photocatalytic activity in degradation of Rhodamine-B(RhB) under 350W Xe lamp light irradiation, and nearly 95.6% of RhB was degraded within 60 min.