Study On Preparation And Photocatalytic Properties Of TiO₂-based Composites

From a global perspective,people are in trouble of environmental pollution and energy shortages.So in recent years,more and more efforts have been focused on the degradation of pollutants and the development of renewable clean energy technologies.Innovative technologies to degrade various pollutants and produce fuel alternatives will become the main research direction now and in the future.Up to now,the use of composite semiconductor photocatalysts to degrade pollutants under sunlight irradiation and the decomposition of water to produce hydrogen has become one of the promising strategies.In this paper,the semiconductor TiO₂ was used as the main research object and the composite semiconductor photocatalysts were prepared based on it.The photocatalytic properties and catalytic mechanism of the as-prepared photocatalysts were further studied.The main research contents include:Using P25 and tetrabutyl titanate as Ti source,the simple hydrothermal methods were used to prepare nano TiO₂ with various morphologies including tube,ribbon,and flower shapes by changing the reaction conditions.After that,XRD,SEM,DRS,BET and other characterization methods were used to determine and analyze the obtained products.Finally,the product was applied to the reduction of Cr（VI）ions and the hydrogen production by photolysis of water for evalutaing the photocatalytic activities,and the product with flower-like morphology exhibits the best activity.The flower-like nano-TiO₂ sample with the best photocatalytic activity in the previous step was selected as the substrate for the further preparation of the composite photocatalyst.In order to compensate the defects of TiO₂,Cu₂O with a suitable band gaps was introduced as composite materials.A variety of characterization methods have been applied and the results prove that the two semiconductors are combined into a new type of photocatalyst Cu₂O/TiO₂.The photocatalytic activity of this photocatalyst was evaluated by degrading methyl orange,methylene blue,and rhodamine B under visible light irradiation.The results show that the activity the Cu₂O/TiO₂ composite photocatalyst is much higher than that of a single TiO₂ under full light irradiation.Flower-like nano-TiO₂ was still used as the composite substrate and the simple hydrothermal method was also used.In this experiment,it is CdSe that was selected to compound with TiO₂ because the two semiconductors are suitable to form a type-II heterostructures.Four CdSe/TiO₂ composite materials with different CdSe content were synthesized by changing the amount of cadmium chloride added.Through the photocatalytic hydrogen production test,the maximum hydrogen production of CdSe/TiO₂ composite materials under simulated sun light and visible light is 41.22mmolg^-1h^-1 and 4.39 mmolg^-1h^-1,respectively.The hydrogen production activity was not reduced significantly after four cycles of experiments show that the as-prepared composite photocatalysts are very stable.