Synthesis,Modification Of TiO₂ Nanomaterials And Their Photocatalytic Activity

Energy and environment is closely related to human life.However,with the rapid development of society,it becomes the main factors restricting the sustainable development of human society.In recent years,semiconductor photocatalytic technology is the main way to solve the energy and environment problem.It uses photo-carrier generated semiconductor materials' absorption of light.Then the pollutants can be removed through a series of complex chemical reactions.Semiconductor photocatalytic technology has received extensive attention due to its non-toxic,efficiency,selective and so on.TiO₂ material is the most widely used semiconductor materials.However,there are some defects in TiO₂ itself.Firstly,it has a low utilization efficiency of solar energy due to its wide band gap.Secondly,it has a low quantum efficiency due to the high recombination rate of its photo-induced carriers.Thirdly,the separation,regeneration and recycling performance of TiO₂ is poor.The above factors restrict the application of TiO₂ photocatalysts.In this paper,our main ideas are tuning the composition,structure,and property of TiO₂ material,and developing highly photocatalytic activity semiconductor photocatalyst with modifying,compounding,doping to absorb visible light and to enhance photocatalytic activity.Here is the main content:?1?This paper presents controllable growth and photocatalytic activity of TiO₂ hierarchical nanostructures by solvothermal method at different temperatures.In the absence of glycerol,the products are only TiO₂ spheres,while the glycerol is present,all the products are in the form of hierarchical TiO₂ structures.The photocatalytic activities of the photocatalysts are evaluated by the photodegradation of Rhodamine B?RhB?under UV light irradiation.The TiO₂ samples exhibit high activity on the photodegradation of RhB,which is higher than that of the commercial P25.The enhancement in photocatalytic performance can be attributed to the synergetic effect of the surface area,crystallinity,band gap and crystalline size.Subsequently,novel dahlia-like TiO₂ structures were successfully synthesized by an ethylenediamine?EDA?-assisted hydrethermal method.The EDA served as ligand and facilitated the growth of dahlia-like TiO₂ structures.Particularly,the dahlia-like TiO₂ structures were built by two-dimensional?2D?thin nanosheets,which interconnected with each other.In addition,the dahlia-like TiO₂ structures own relatively large specific surface areas of 158.85 m2/g.Furthermore,the dahlia-like TiO₂ structures exhibit higher photocatalytic activity than that of commercial P25 for degradation of RhB under UV light irradiation.The enhanced photocatalytic activity is due to the synergetic effect of the architecture and high BET surface area of the photocatalyst.?2?Preparation of flower-like CeO₂/TiO₂ heterostructures as photocatalysts was successfully obtained by a simple two-step solvothermal/hydrothennal method.The as-prepared sample consisted of the oriented aggregation of small CeO₂ nanoparticles supported on the self-assembled nanorods of hierarchical flower-like TiO₂.Compared with pure CeO₂,pure TiO₂,the mixture of CeO₂/TiO₂ and commercial P25,the flower-like CeO₂/TiO₂ heterostructures exhibited markedly enhanced photocatalytic activity in the degradation of RhB under UV light irradiation.The enhanced photocatalytic activity of flower-like CeO₂/TiO₂ heterostructures could be attributed to the improvement of charge separation derived from the coupling effect of TiO₂ and CeO₂ heterostructures.Subsequently,CeO₂/TiO₂ microspheres were obtained by adjusting the pH value of the reaction solution during the hydrothermal process.As the pH value changes,the porphology of the samples will be change.The results showed that the as-prepared CeO₂/TiO₂ microspheres significantly enhanced the UV photocatalytic activity compared with pure CeO₂ and TiO₂.The optimal pH value for the photocatalytic activity of the CeO₂/TiO₂ microspheres was determined.The CeO₂/TiO₂ microspheres?pH=9.5?exhibited the highest photocatalytic activity,which shows a reaction rate constant as high as 0.04 min-1,2.1 times higher than that of pure TiO₂.The synergic between the CeO₂ and TiO₂ were found to lead to an improved photo-generated carrier separation and hence the photocatalytic activities of the CeO₂/TiO₂ microspheres were increased.?3?Mesoporous Ce-doped TiO₂ nanoparticles with different content of Ce are prepared by one-step hydrothermal method.The results show that TiO₂ doped with Ce can reduce the crystallite size.Under UV irradiation,the Ce-doped TiO₂ samples exhibit much higher photocatalytic activity than pure TiO₂ and commercial P25 for the degradation of Rhodamine?RhB?.The maximum photocatalytic reaction rate constant for Ce-doped TiO₂ sample is obtained as 0.021 min-1.The unique photocatalytic properties of Ce-doped TiO₂ are attributed to the improvement of photogenerated electron-hole pairs separation efficiency and formation of more reactive oxygen species owing to the presence of Ce3+/Ce4+.A degradation mechanism is proposed for the degradation of RhB for Ce-doped TiO₂ photocatalyst under UV light.