Synthesis And Photocatalytic Performance Of Lanthanum-doped TiO₂ Nanorods Through The Sol-gel-hydrothermal Method

In this paper,anatase 0.4% La-TiO2 nanorods with more regular shape,the diameter of about 20-30 nm,the length of about 200 nm and better dispersion were successfully synthesized,using tetrabutyl titanate as a precursor through the sol-gel-hydrothermal method.The effects of sol-gel process conditions,calcination temperatures,hydrothermal conditions and lanthanum doping amounts on the morphology,crystal structure,UV-Vis absorbance and photo-catalysis capability of TiO2 powders have been investigated.The results show that the optimum technological parameters for preparing TiO2 nanoparticles through the sol-gel method are listed as follows: the molar ratio of tetrabutyl titanate / deionized water / anhydrous ethanol / glacial acetic acid is 1:0.4:3.5:0.5,the PH value is 2.5,the gel temperature is 20-26 ?,the gel time is about 8 h,and the gel calcination temperature is about 450 ?.Since the lanthanum may inhibit the TiO2 crystal growth,the optimum gel calcination temperature after lanthanum doping is 500? and the optimum doping amount of lanthanum is 0.4%.The subsequent hydrothermal treatment can induce the phase transition of TiO2 from nanospheres to nanorods,which can significantly improve both the intensity and width of absorbance spectral peak.Hydrothermal treatment method shows a better capability than lanthanum doping to improve the UV-Vis light absorption intensity,as well as the light absorption range of TiO2.As a result,it can more efficiently improve the photo-catalytic degradation efficiency of methylene blue.The light-absorption threshold of TiO2 nanorods prepared at 450 ? gel calcination temperature and by the subsequent hydrothermal treatment was red-shifted to 548 nm,the band gap was reduced to 2.28 eV,and the photodegradation rate of methylene blue for 60 min was increased to 98.0%.The light-absorption threshold of 0.4% La-TiO2 nanospheres prepared at 500 ? gel calcination temperature was red-shifted to 478 nm,and the light-absorption threshold of 0.4% La-TiO2 nanorods prepared by the subsequent hydrothermal treatment was red-shifted to 555 nm,the band gap was reduced to 2.23 eV,and the photodegradation rate of methylene blue for 60 min was increased to 98.9%.The research results in this thesis are of great significance to effectively solve the problem of organic printing and dyeing wastewater.