The Photochemical Behavior Of Typical VOCs Pollutants On The Surface Of SnO₂Nano-structure

Due to their high volatility and toxicity, volatile organic compounds (VOCs) are a great threaten to both environment and human health, whose photochemical behaviors varies in different environmental medium. The troposphere is called global photocatalytic reactor where light irradiation and solid-phase particles are abundant, which provide powerful activation energy and a reactive substrate or medium for photochemical reactions. Consequently, it’s of great deals of importance to do researches into the heterogeneous photochemistry of VOCs on solid-phase particles present in the troposphere. In this work, toluene and acetone were chosen as representative pollutants of VOCs to investigate the photochemical behavior on the surface of SnO2nano-structures with FTIR, which were also compared to the UV photolysis. In this dissertation, the following works were carried out:(1) SnO2nano-structure fabrication. SnO23D hollow spheres and1D nanorods were synthesized via hydrothermal and the carbon template method, respectively. Morphology, structure, chemical composition and optical properties were characterized by means of field emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), X-rays photoelectron spectroscopy (XPS), photoluminescence spectra (PL), UV-Vis diffusive reflectance spectra (DRS), surface photovoltage spectroscopy (SPS) etc.(2) The UV photolysis of toluene without adding SnO2was investigated by in situ FTIR. Results indicated that toluene was degradable by UV irradiation. The main intermediate detected were benzaldehyde and benzoic acid, while the main oxidation products were CO2, H2O and CO but benzene and formic acid were also detected.(3) The photochemical behavior of toluene on the surface of SnO23D hollow spheres under UV irradiation was studied by in situ FTIR. The findings implied that toluene was firstly converted into benzaldehyde, which would be further converted into benzoic acid. Finally benzoic acid was transformed into acetic acid and CO2, H2O and CO. (4) In situ FTIR was employed to monitor the UV photolysis of acetone without SnO2. During the photolysis, acetaldehyde was emerged only as a transient product which would be finally converted to be ethylether, CO2, CO and H2O.(5) The photochemical behavior of acetone under UV irradiation on surface of SnO2nanorods was also inspected with help from in situ FTIR. The observation demonstrated that on surface of SnO2nanorods, acetone was firstly degraded into acertic acid and ether, which would be further converted into formic acid, CO2, H2O and CO.