Studies On Preparation, Characterization And The Photocatalytic Behaviors Of ZnGa₂O₄Nanocrystals

Spinel metal oxide photocatalyst,d10configuration p-block element Ga containing ZnGa2O4widely used in the field of conductive material,the light-sensitive material and so on. Many attention and concern have attracted in the research of water splitting,photoreduction of CO2and photocatalytic degradation of organic pollutants. In the present work,zinc gallate spinel were prepared by a coprecipitation route and the samples were well characterized and photocatalytic properties were investigated. We selected4-Chlorophenol(4-CP) and toluene as the target and investigated the catalytic activity of the photocatalysts in liquid-solid phase or gas-solid phase,through the in situ infrared spectroscopy researched photocatalytic toluene reaction courses. In this dissertation,the following three aspects investigations were carried out:(1) Nanosized powders of single-phase zinc gallate spinel were successfully prepared by a coprecipitation route. Morphology and structure of ZnGa2O4nanocrystals were detected by these means such as X-ray diffraction(XRD), Scanning electron microscopy(SEM) and Specific surface area and pore size analyzer characterization methods.The elemental composition and valence state on the surface could be measured by Energy dispersive X-ray spectrum(EDS) and X-ray photoelectron spectroscopy(XPS).And the photoelectric properties were detected through UV-vis diffuse reflectance spectrum(DRS)、Surface photo voltage (SPV) and Fluorescence(FL) technology.(2)Application of the target pollutant compared the efficiency of the process of natural degradation,direct photolysis, photocatalytic degradation of4-CP.4-CP was degraded largely after UV light irradiation for180min over the photocatalyst at room temperature in air. The peaks224nm and278nm were assigned to the UV-vis absorption spectra of4-CP characteristic peaks. It could be observed that the original peaks disappeared and no new peak could be found after the photocatalytic oxidation reaction of240min, indicating the aromatic rings did not exist. For comparision,4-CP was found to be stable and no physicochemical degradation without UV light irradiation in the catalyst-loaded reactor. A shift of the characteristic peaks moved into258nm was observed when it was illuminated in the absence of catalyst. The new formation peak became stronger along with the reaction time increased. Thus, new aromatic ring compounds have been formed under UV light illumination. (3) The in-situ infrared spectroscopy was used to investigate the photocatalytic reaction of toluene simulated indoor pollutant under UV irradiation.In the presence of the catalyst ZnGa2O4nanocrystals, benzaldehyde and benzoic acid were mainly toluene photocatalytic degradation generated intermediates. Results show that toluene was mineralized into carbon dioxide and water as the major species, and small amount of carbonmonoxide and acetic acid species were also produced during the reactions.Upon irradiation, the intensity of these bands begins to decrease slowly. After12h prolonged irradiation, the percentage of toluene photocatalytic degradation reaches up to88%, whereas the degradation percentage of toluene over direct UV photolysis reaches to78%。...