Preparation, Microstructure And Photocatalysis Of Nano-TiO₂Doped With Rare Earth

The semiconductor materials of nano-Ti02photocatalysis had become the research focus of the majority of scholars that due to its application in environmental protection, clean, and no secondary pollution. However, because of its forbidden band is relative wide only use UV excite which limit its used, so many scholars have studied how to modified it. The energy levels of rare earth relative rich, nano-TiO2photocatalysis doped with Sm3+, Y3+, Pr3+, Gd3+, Sm-Gd, Sm-Y was prepared by sol-gel method in this study and the photocatalystic activity under ultra-violet light was evaluated by photocatalystic degradation of methyl blue. The relationship between nano-TiO2photocatalysis properties and its structure or microstructure by the testing techniques such as TG-DTA, XRD, TEM, UV-Vis, IR. The impact of the external environment to photocatalytic test studied by orthogonal experimental. Explore the photocatalytic mechanism of nano-TiO2doped with rare earths and the reaction kinetics of photocatalytic of doped nano-TiO2had be studied.During the study of nano-TiO2doped with Sm3+, nano-TiO2doped with Sm3+was prepared by sol-gel method and the photocatalystic activity under ultra-violet light was evaluated by photocatalytic degradation of methyl blue. Explore the impact of heat treatment temperature, content of Sm3+, external environment to photocatalytic test and microstructure to nano-TiO2photocatalysis properties by modern measurement technology. The heat treatment method of photocatalyst was at520℃for2h in this article which determined by the results of TG-DTA and XRD. The average particle size for undoped TiO2was22.01nm, the size for the Sm3+doped TiO2samples were smaller than the undoped TiO2. The orthogonal experimental results showed that the influence order of the initial concentrations of methylene blue solution, catalyst dosage and pH value of the solution to nano-TiO2photocatalysis properties was:the initial concentrations of methylene blue solution>catalyst dosage>pH value of the solution. The optimum external environment of doped nano-TiO2was:0.25g (catalyst)/50ml (MB solution), pH=8, initial of concentration MB=5mg/L. With the increase of amount of Sm3+doped the degradation of those samples first increase and then reduce, the degradation of the optimal doped sample S3was95.16%which amount for Sm3+-doped was0.1mol%. The photocatalyst on methyl blue degradation coincide first order dynamic equation. The rare earth doped made the TiO2UV-vis absorption edges had a different degree of redshift, band gap decrease, and make effective use of ultraviolet-visible light. The shift amount of S3was20nm. The TEM result showed that the rare earth doped TiO2photocatalyst in this study were spherical morphology with particle sizes of20nm. The main phase of S3was anatase which belong to the tetragonal system and coincide XRD result. Some Sm2O3particles attached to the surface of the TiO2particles caused lattice distortion.During the study of nano-TiO2doped with Y3+, nano-TiO2doped with Y3+was prepared by sol-gel method and the photocatalystic activity under ultra-violet light was evaluated by photocatalytic degradation of methyl blue. Explore the impact of content of Y3+, external environment to photocatalytic test and microstructure to nano-TiO2photocatalysis properties by modern measurement technology. The average particle size for undoped TiO2was22.01nm, the size for the Y3+doped TiO2was smaller than the undoped TiO2. The orthogonal experimental showed that the influence order of the initial concentrations of methylene blue solution, catalyst dosage and pH value of the solution to nano-TiO2photocatalysis properties was:the initial concentrations of methylene blue solution>pH value of the solution> catalyst dosage. The optimum external environment of doped nano-TiO2was:0.25g (catalyst)/50ml (MB solution), pH=8, initial of concentration MB=5mg/L the result same to Sm3+doped samples. With the increase of amount of Y3+doped the degradation of those samples first increase and then reduce, the degradation of the optimal doped sample Y3was90.68%which amount for Y3+doped was0.2mol%. The photocatalyst on methyl blue degradation coincide first order dynamic equation. The rare earth doped made the TiO2UV-vis absorption edges had a different degree of redshift, band gap decrease, and make effective use of ultraviolet-visible light. The shift amount of Y3was18nm. The TEM showed that the rare earth doped TiO2photocatalyst in this study were spherical morphology with particle sizes of18nm. The main phase of Y3was anatase which belong to the tetragonal system and coincide XRD result. Some Y3+enter the crystal lattice of TiO2and caused lattice distortion.During the study of nano-TiO2doped with Pr3+, nano-TiO2doped with Pr3+was prepared by sol-gel method and the photocatalystic activity under ultra-violet light was evaluated by photocatalytic degradation of methyl blue. Explore the impact of content of Pr+and microstructure to nano-TiO2photocatalysis properties by modern measurement technology. The average particle size for undoped TiO2was22.01nm, the size for the Pr3+doped TiO2was smaller than the undoped TiO2With the increase of amount of Pr3+doped the degradation of samples first increase and then reduce, the degradation of P3was91.16%which amount for Pr3+doped was0.05mol%. The photocatalyst on methyl blue degradation coincide first order dynamic equation. The rare earth doped made the TiO2UV-vis absorption edges had a different degree of redshift, band gap decrease, and make effective use of ultraviolet-visible light. The shift amount of P3was17nm. The TEM result showed that the rare earth doped TiO2photocatalyst in this study were spherical morphology with particle sizes of20-30nm. The main phase of P3was anatase which belong to the tetragonal system and coincide XRD results. Some Pr3+enter the crystal lattice of TiO2and some Pr3O3particles attached to the surface of the TiO2particles caused lattice distortion.During the study of nano-TiO2doped with Gd3+, nano-TiO2doped with Gd3+was prepared by sol-gel method and the photocatalystic activity under ultra-violet light was evaluated by photocatalytic degradation of methyl blue. Explore the impact of content of Gd3+and microstructure to nano-TiO2photocatalysis properties by modern measurement technology. The average particle size for undoped TiO2was22.01nm, the size for the Gd3+doped TiO2was smaller than the undoped TiO2. With the increase of amount of Gd3+doped the degradation of samples first increase and then reduce, the degradation of G3was94.51%which amount for Gd3+doped was0.1mol%. The photocatalyst on methyl blue degradation coincide first order dynamic equation. The rare earth doped made the TiO2UV-vis absorption edges had a different degree of redshift, band gap decrease, and make effective use of ultraviolet-visible light. The shift amount of G3was20nm. The TEM result showed that the rare earth doped TiO2photocatalyst in this study were spherical morphology with particle sizes of20-30nm. The main phase of G3was anatase which belong to the tetragonal system and coincide XRD result. Some Gd3+enter the crystal lattice of TiO2caused lattice distortion.During the study of co-doped nano-TiO2, nano-TiO2doped with Sm-Gd and Sm-Y were prepared by sol-gel method and the photocatalystic activity under ultra-violet light was evaluated by photocatalytic degradation of methyl blue. Explore the impact of doped behavior of rare earths and microstructure to nano-TiO2photocatalysis properties by modern measurement technology. XRD results showed that the average particle size for undoped TiO2was22.01nm, the size for the co-doped were smaller than the undoped TiO2. The rare earths doped caused lattice distortion, Sm-Gd co-doped increase of TiO2lattice volumes, Sm-Y co-doped decreased of TiO2lattice volumes. The results of photocatalytic experiments showed that the photodegradation take place of the surface of TiO2.The experimental mechanism of improved photocatalytic efficiency photocatalyst for Sm3+, Y3+, Pr3+, Gd3+mono-doped TiO2were:some rare earth enter the crystal lattice of TiO2caused lattice distortion and surface sensitization. For example, Sm3+, Y3+, Pr3+and Gd3+enter the clearance of crystal lattice or some Y3+replaced the position of Ti4+caused lattice distortion. The lattice distortion caused TiO2lattice missed one electron, the oxygen vacancy defects formed from the crystal lattice to maintain the charge equilibrium, but the vacancy be bounded by the rare earth ion. Accorded to the theory of knowledge, the additional level of the vacancy in the band at the bottom, the oxygen vacancy required a lower energy captured electrons in the valence band to disappear, so reduced the probability of the electron and hole composited, and the quantum efficiency of TiO2be increased. Rare earth elements contain f electrons which beneficial to improve the adsorption of organic pollutant. So the adsorption of organic pollutant of TiO2be improved by some Sm2O3and Pr2O3enrichment on the surface of TiO2that improved the efficiency of TiO2photocatalysis.The experimental mechanism of improved photocatalytic efficiency photocatalyst for Sm-Gd co-doped samples was:some Sm3+attached to the surface of TiO2particles formed on the surface of the photosensitive structure which to improve the adsorption of organic pollutant. At the same time the absorption spectra for Sm3+were362.5nm、374.5nm402.Onm, so Sm3+absorption the visible light and than passed to the TiO2to improve the number of photoelectron or photo generated hole. Gd3+enter the clearance of crystal lattice caused lattice distortion. So the lattice distortion caused TiO2lattice missed one electron formed oxygen vacancy defect in order to maintain the charge equilibrium, but the vacancy be bounded by the rare earth ion. Accorded to the theory of knowledge, the additional level of the vacancy at the bottom of the band, the oxygen vacancy required a lower energy captured electrons in the valence band to disappear, so reduced the probability of the electron and hole composited, and the quantum efficiency of TiO2be increased. The experimental mechanism of improved photocatalytic efficiency photocatalyst for Sm-Y co-doped samples were:some Sm3+and Y3+attached to the TiO2particles which hindered the growth of TiO2crystal and lattice be smaller caused lattice distortion. At last reduced the recombination rate of photoelectron and photo generated hole. In other side Sm3+and Y3+absorption the visible light and than passed to the TiO2to improve the number of photoelectron or photo generated hole. At the same time rare earths improve the adsorption of organic pollutant. In summarized co-doped photocatalyst could in a short period of time succeed to the photodegradation of methylene blue.