Preparation Of Rare Earth-doped TiO₂ Nanocrystals And Studies On Their Photocatalytic Performances

In recent years,semiconductor photocatalysis technology is a kind of environmental pollution treatment technology with great development potential.It has become a research hotspot because it can use solar energy to degrade organic pollutants.Therefore,it is of great significance to develop efficient photocatalytic materials.Titanium dioxide（TiO₂）is widely used because of its excellent chemical stability,non-toxic,no secondary pollution and other advantages.However,TiO₂has low utilization of solar energy and low quantum efficiency,which seriously limits the large-scale practical applications.Therefore,it is urgent to take effective measures to improve its photocatalytic ability.In this paper,pure TiO₂prepared under different reaction conditions,single and double doped TiO₂nanocrystals with different concentrations of rare earth elements were available by one-step hydrothermal method.The samples were characterized by various characterization methods,and the photocatalytic activity of degradation of Rhodamine B（RhB）under visible light irradiation was also studied.The main conclusions are as follows:（1）TiO₂ nanocrystalline photocatalysts with different reaction conditions（tetrabutyl titanate（Ti（OBu）₄）dosage,temperature and time）were prepared by hydrothermal method.The results showed that the transformation of TiO₂nanocrystals from nanorods to spheres was realized with the increase of titanium source.Besides,the crystal form of the samples was tetragonal rutile phase with high purity.In the process of synthesizing TiO₂nanocrystals,the absorption intensity in the ultraviolet region can be greatly affected by changing the amount of tetrabutyl titanate,temperature and time.The results of photocatalytic experiments showed that the change of reaction conditions has a certain effect on the photocatalytic degradation activity.（2）Single rare earth element（Ho,Yb,Pr or Y）doped TiO₂photocatalysts were prepared by hydrothermal method.The results showed that the agglomeration of TiO₂nanocrystals can be significantly improved by appropriate rare earth doping,but the single rare earth doping did not change the crystal structure and morphology of the samples.In addition,different rare earth ions doping can improve the UV-Vis absorption intensity and enhance the photocatalytic activity.The results of photocatalytic experiments showed that the photocatalytic activity of Pr-TiO₂doped with 5%rare earth element was the best,the degradation rate was 75.1%,which was 12.4%higher than that of pure TiO₂（degradation rate was 62.7%）.The reaction rate constant was 1.4 times higher than that of pure TiO₂.The results showed that single doping can improve the photocatalytic activity of TiO₂.（3）TiO₂ photocatalysts doped with double rare earth elements（Ho/Yb,Ho/Pr,Ho/Y,Yb/Pr,Yb/Y or Pr/Y）were prepared by hydrothermal method.The results showed that rare earth co-doping still did not change the crystal form and morphology of the samples,but it can refine the grain size of TiO₂and reduce the particle size.And,it can reduce the agglomeration phenomenon of the sample and make it better dispersibility.In addition,the co-doped TiO₂samples can significantly improve the absorption intensity in the ultraviolet visible region and broaden the visible light response range,which will be conducive to the improvement of photocatalytic activity.These phenomena can be conducive to the improvement of photocatalytic activity.The results of photocatalytic experiments showed that the co-doped TiO₂can effectively improve the photocatalytic activity than the single component doped TiO₂.The photocatalytic activity of（Ho,Pr）-TiO₂with Ho/Pr molar ratio of 1:1 was the best when the total doping amount of rare earth was 5%,and the degradation rate was 87.6%.The solution had changed from red to colorless.Compared with pure TiO₂,the photocatalytic degradation rate was increased by 24.9%,and the reaction rate constant was2.1 times of pure TiO₂.The results showed that co-doping can significantly improve the photocatalytic activity of the samples.