| Because of its excellent photoresponse performance, TiO2 has a great practical utility in the field of photocatalytic degradation of organic pollutant and photoelectric conversion. At the same time, its various crystal structures and morphology enabled it own a huge scientific value. The research of new morphologies, new crystal structure and improving the photocatalytic properties of titanium dioxide by doping ions and compositing with other compound has been a hot and important topic. By combining the methods of precipitation and hydro-thermal synthesis, we prepared TiO2 nanosheets. In the process, we explored the reaction condition to form TiO2 nanosheets and analyzed the influence of the reaction conditions on TiO2 nanosheets. To further improve the photocatalytic properties of the product, we composited it with graphene oxide by a hydrothermal reduction process. Then the influence of the compositing condition was investigated and the mechanism of how RGO improves the photocatalytic properties researched.(1) Ti(OH)4 was prepared by hydrolysis of Ti(SO4)2. Ti(OH)4 and NaOH solution were respectly used as precursor and reaction medium, by controlling the concentration of NaOH solution, the hydrothermal reaction time and temperature, amorphous TiO2 of layered lamellar was prepared. In order to guarantee the products' photocatalytic properties, we treated them with HNO3 to exchange Na+ in the products. Then the products were calcined to get anatase. The results showed that the concentration of NaOH solution influence the morphology of the product. The hydrothermal reaction temperature and hydrothermal reaction time can affect the thickness and size of the nanosheets. Calcination temperature and calcination time mainly affects the crystal size and the number of crystal defects. The product underwent the hydrothermal reaction at 150 ? for 96 h in 6mol / L NaOH solution and was calcined for 3h at 400 ? had the best lamellar structure and photocatalytic effect.(2) To prepare TiO2 / RGO composites, after ion exchange, the product we dried and mixed with graphene oxide solution. The mixture reacted in citric acid solution for hours and then calcined at the protection of N2. In this experiment, we investigated the proportion of precursor and graphene, acidity of reaction liquid, hydrothermal reaction time and hydrothermal reaction temperature on product's morphology and photocatalytic properties. It revealed that photocatalytic activity of TiO2/RGO composites increased more than 20% in contrast with pure TiO2. The photocatalytic effect is best when the mass ratio of GO and Ti(OH)4 precursor was 1%. The optimal reaction conditions is 80?in the solution of 0.1g / ml of citric acid for 8h.(3) Based on the above experiments, we analyzed the effect of reducing graphene oxide: on the one hand, the composite of RGO/TiO2 changed the crystal structure after calcination at 400 ?, thus forming a mixed crystal structure of anatase and rutile enhanced the photocatalytic properties; on the other hand, the morphology of the composite is changed from the original sheet structure into rod-like structure whose surface was rough, so that the the specific surface area increased a lot which can enhance the photocatalysis performance. In addition, the reduction of graphene oxide enhanced the conductivity a lot which is helpful to promote the lifecycle of the photo-generated electron- hole pairs and enhance the redox reaction efficiency. |
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