Preparation, Characterization And Photocatalytic Properties Of A Series Of Titanium Dioxide-based Composite Photocatalysts

Photocatalysis technology is considered to be the most promising new technology of controlling environmental pollution due to the photodegradation progress of organic pollutants in the field of environmental protection since the1990s. With the development of photocatalysis technology, as a common photocatalysts, TiO2has the advantages of non-toxicity, cheapness and good chemical stability. However, TiO2can only use the3%ultraviolet part of the solar energy due to its wide band gap and its low quantum yield. Hence, in order to develop more efficient photocatalysts with high quantum yield and that can be excited by visible light, researchers employed a variety of modification techniques to modify TiO2to improve the photocatalytic activity. In addition, graphene has become a reaserch hotspot because of its large theoretical specific surface area and unique electron transport properties in recent years. So the TiO2/graphene nanocomposite photocalysts not only increase adsorption of pollutant organics but also facile charge transportion and separation, which expand light absorption range and enhance photocatalytic activity.In this thesis, based on the study of titanium dioxide photocatalytic mechanism, a series of TiO2/graphene-based nanocomposites were prepared, and these photocatalysts were expected to show an enhancement in photodegradation efficiency under visible light illumination. The detailed research works are shown as follows:1. Based on the study of titanium dioxide photocatalytic mechanism, our research goal is to explore the photocatalytic mechanism of titanium dioxide/graphene through adding various amounts of hydroxyl radical trapping agent of tert-butanol and hole scavenger of Na2SO3in the photocatalytic reaction system and then investigating their impact on the rate of photodegradation of the dye. The results will determine the active species in the processe of photocatalytic oxidation, which can also help deepen titanium dioxide photocatalytic mechanism.2. Firstly TiO2/Graphene nanocomposites were prepared by hydrothermal synthesis using titanium tetrachloride and graphene oxide as the precusors. And the iodine was then introduced into TiO2/graphene nanocomposites through the thermal reduction treatment with55-58%hydroiodic acid, forming HI acid-treated TiO2/graphene nanocomposite (HI-TiO2/rGO). Photocatalytic experiments demonstrated that for HI-TiO2/rGO, the adsorptive capacity of Rhodamine B molecules has been enhanced, and the visible light photocatalytic effect has also been significantly improved, which is associated with stronger reduction degree of graphene after HI acid treated.3. The precursor solutions of titania nanotubes were prepared using tetrabutyl titanate as the titanium source and ethylene glycol as a solvent in an oil bath at170℃for2h firstly. And then the glycol solution was mixed with graphene oxide, and the mixture was transferred to autoclave for hydrothermal reaction at200℃for24h in alkaline conditions, getting monoclinic phase titania nanotube/graphene composite photocatalyst. The effects of the hydrothermal reaction temperature and the concentration of NaOH aqueous solution on the sample morphology and photocatalytic efficiency were explored. Experimental results showed that when the hydrothermal temperature was200℃and NaOH solution concentration was8mol/L, the photocatalysts have best photocatalytic activity under ultraviolet light.