Study On The Preparation And Modification Of Nanometer Strontium Titanate

To prepare suitable photocatalyst is help to solve increasingly environmentpollution problems. The catalyst can not only promote efficiently to degrade organicpullutants in wastewater in sunlight, but also there is no the secondary pollution and thecost is low. As a semiconductor photocatalyst,SrTiO₃,which possess suitable bandgapenergy（Eg） and high stability,has high potential researching value and wideapplication foreground. However, The problems, which are how to improve theprepared method, how to make full use of the visible light, and how to recover thecatalyst should be solved.In this thesis, tartaric acid as a solvent,dispersant and stabilizer in the modifiedSol-gel method. In the preparation procedure,the dosage of tartaric acid and H2O on theproperties of the SrTiO₃was researched. The results indicated the crystalline size was20.8nm, degree of crystallinity was89%and degradation ratio of MB was40%whenthe mole ratio of Sr²⁺to tartaric acid was1:4and dosage of H2O was20mL. Thisimproved method was simple,low cost,without toxin or stimulation and friendly toenvironment.Ce⁴⁺doped SrTiO₃photocatalyst was prepared by the improved Sol-gel method. Theprepared photocatalyst was charactered by XRD, IR, BET, SEM, XPS and UV-vis andits catalytic activity was investigated by decomposing of methylerie blue.The resultsindicated that the crystalline size decrease, specific surface area increased andrecombination of photo electrons and holes weaken when Sr²⁺was replaced by Ce⁴⁺.Doping Ce⁴⁺increased the amount of the adsorption oxygen and H2O on thephotocatalyst surface, the increase leaded to the increase of catalytic active center.Meanwhile,4f energy degree of Ce⁴⁺reduced the band gap of SrTiO₃and enhanced thephotoelectrons by the reduction of Ce⁴⁺to Ce³⁺.consequently,photoelectron lifetimeand photocatalytic activity of the SrTiO₃doped Ce⁴⁺were increased. The highestactivity was obtained and the degradation ratio of MB was98.7%as SrTiO₃doped3mol%Ce⁴⁺.SrTiO₃/SrFe₁₂O₁₉photocatalyst was also prepared by the improved Sol-gel methodand its properties was characterized by the same way with Ce⁴⁺doped SrTiO₃.Theresults indicated that most SrFe₁₂O₁₉was capsuled in the SrTiO₃, with less expressionon surfaces.The specific surface area of SrTiO₃/SrFe₁₂O₁₉was increased and it’s absorption peak moved into visible light region, those in favour of improvement of theactivity of the photocatalysts. The highest activity was obtained and the degradationratio of MB was98.6%as SrTiO₃doped25%SrFe₁₂O₁₉.At the same time, it was easyto be separated and recycled from reaction system.The repeated tests indicate thatSrTiO₃/SrFe₁₂O₁₉could be used repeatedly and the degradation ratio of MB was stillabove80%after repeating5times.