| Among lots of photocatalytic material, TiO2is supposed to be kind of promisingcatalysts because of its lowcost, harmless, good chemical stability and excellentphotocatalytic activity. However, the photoproduced electrons and holes in TiO2mayexperience a rapid recombination leading to poor quantum efficiency of photocatalysis,which diminishes the efficiency of the photocatalytic reaction significantly.In order to improve the photocatalytic activity of TiO2, it is necessary to improve thequantum efficiency by inhibiting the recombination of electrons and holes. Through thenonmetallic elements doped TiO2, it can effectively extend the life of thephoto-generated electron-hole pairs, and then enhancing the ability of TiO2photocatalytic oxidation. In addition, as a novel two-dimensional material, graphenepossesses excellent electrical and optical properties and outstanding mechanicalproperty. Recently, due to unique advantages of graphene, modifying TiO2withgraphene has attracted a great deal of attention. Therefore, in this thesis, RGO/TiO2composites and fluorizated TiO2were synthesized and investigated. The main results areas follows:(1) Using tetrabutyl orthotitanate as Ti source, hydrofluoric acid as F source, wellcrystallized fluorizated TiO2hollow microspheres have been synthesized via asolvothermal process. By analyzed the different samples, the influences of reacting timeand initial F/Ti molar ratio were discussed. The results indicated that the hollowfluorizated TiO2microspheres were achieved by Ostwald ripening under solvothermalconditions, while the presence of hydrofluoric acid will have an impact on the TiO2hollow structure. XPS, FTIR analysis shows that the fluoride ions in the surface of TiO2existed with chemical adsorption, forming≡Ti-F group. Compared to pure titania, thefluorizated TiO2hollow microspheres showed a much higher degradation efficiencyattributed to the unique structure of the hollow microsphere and the fluorinemodification.(2) Graphene oxide was synthesized from graphite powder utilizing modifiedHummers method. The microstructural of graphene oxide was characterized by a seriesof analysis, paving the way for the subsequent study RGO/TiO2composites. The resultsindicated that graphene oxide has many oxygen containing functional group, such ascarboxyl, oxhydryl, and epoxy group, which can act as nucleation sites. The preferential nucleation on the surface of GO combined with the modulated growth of TiO2nucleiled to the formation of a mesoporous anatase nanostructure assembled on the RGO.(3) RGO/TiO2composites were synthesized with a hydrothermal method under theinterruption of boric acid, using graphene oxide and titanium ammonium fluoride asprecursors. The influence of initial graphene oxide content, hydrothermal temperatureand time on the structure and photocatalytic activity of RGO/TiO2composites wasinvestigated. The results show that both graphene oxide content and the hydrothermalreaction conditions can affect the photocatalytic activity of the obtained RGO/TiO2composites. It can promote the crystallization of TiO2and increase photocatalyticactivity of RGO/TiO2composites by improving the hydrothermal temperature. Theinfluence of hydrothermal time on the crystallization of TiO2was not obvious. However,the structure of graphene in RGO/TiO2composites can break down increased withhydrothermal reaction time. As a result, the photocatalytic activity of RGO/TiO2decreased with the increasing of hydrothermal time. As a result, the photocatalyticactivity of RGO/TiO2composites decreased with the increasing of hydrothermal time.So,180oC and6h were selected as the best initialization hydrothermal condition. Theincorporation of GO resulted in an increase of the photocatalytic activity of RGO/TiO2composites. Because RGO/TiO2composites possessed great adsorptivity of dyes, andenhanced charge separation and transportation properties simultaneously, comparedwith pure TiO2, the RGO/TiO2composites exhibited excellent photocatalytic activity.There is a synergism between adsorption and photocatalytic degradation under the UVlight irradiation in dye removal by RGO/TiO2composites. |
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