Studies On Preparation Of Bi₂O₃/Bi₂WO₆Nanocomposites Used For Photocatalytic Degradation Gaseous Toluene

With the development of social economy and technology, life becomes more and more convenient, and more people are willing to stay indoors. In recent years, rates of respiratory disease and incidence of allergic responses such as asthma have increased, and people are concerned that some of the increase could be connected with the air quality change inside the house where we living and working. Because of the long term effects of pollutants on humans, the elimination of low concentration gaseous indoor air pollutants is of particular concern. Indoor air pollution is bringing acute health problems to human beings. Toluene is a very important solvent worldwide and occurs naturally in consumer products. Because of its high volatility and wide usage in consumer products, toluene is a threat to human health. Among all the technologies, photocatalysis is becoming more and more popular because of its low cost and high efficiency without derived pollution. For photocatalysis, the key is choosing a good photocatalyst. In this dissertation, we try to study Bi2WO6and modify it for a better activity. We successfully synthesized Bi2WO6and Bi2O3/Bi2WO6heterojunction hollow-like microspheres by using solvothermal method and did systematic characterization on these catalysts. Through in situ FTIR measurement we study their activities on decomposing toluene comparatively. We have carried out the following investigations:(1) We prepared Bi2WO6and Bi2O3/Bi2WO6heterojunction hollow-like microspheres by using solvothermal method. We studied their morphology and composition through scanning electron microscopy (SEM). EDX. X-ray photoelectron spectroscopic analysis (XPS), X-ray diffraction (XRD), transmission electron microscope (TEM) and Fourier transform infrared (FTIR). Through nitrogen adsorption and desorption method, surface and pore structure were investigated. The conclusion is that we successfully synthesized the Bi2WO6and Bi2O3/Bi2WO6catalysts by using solvothermal method with PVP’s existance. And the sample S3(Bi:W=2.8:1in raw materials, Bi2O3/Bi2WO6heterojunctions) has the biggest surface area.(2) The optical properties of the catalysts were examined through diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and surface photovoltage (SPV). We believe sample S3(Bi:W=2.8:1in raw materials. Bi2O3/Bi2WO6heterojunctions) show stronger response in the visible-light region in DRS spectra and better separation rate of electron-hole pairs judging from lower photoluminescence and higher surface photovoltage. (3) We study the photocatalytic activities of the prepared catalysts and the products by decomposing toluene under visible light using in situ FTIR method. The results show that heterojunctions can enhance the activities of catalysts. And the decomposition rate of toluene by using S3(Bi:W=2.8:1in raw materials, Bi2O3/Bi2WO6heterojunctions) under visible light can reach as high as90%in5hours, which is20percentage points higher than by using S1(Bi2WO6). And the products of this reaction are aldehyde species. CO2and H2O.