Study On The Synthesis Of M（Ca, Sr, Ba）TiO₃,Dopping Of CaTiO₃and Their Photocatalytic Performance

Due to its unique structure and excellent catalytic performance, perovskite-type catalystscould be modified by doping to improve its catalytic activity without changing its intrinsicstructure. Herein, modifying perovskite oxide to enhance the photocatalytic performance hasattracted great interest. In this work, CaTiO3with wide band gap was chosen as the hostphotocatalyst, we devoted to narrowing its band gap and improving the photocatalyticperformance by controlling the morphology and doping ions into its bulk lattice. The optimalconditions for preparing the catalyst and the influences of several process parameters on thephotocatalytic performance were investigated. The X-Ray Diffraction (XRD), ScanningElectron Microscope (SEM), Thermogravimetry Analysis-differential Thermal Analysis(TG-DSC), UV-Vis Diffuse Reflectance Spectrophotometry (DRS), UV-Vis Spectrometer andElectronchemical workstation were used to characterize the morphology, microstructureelectrochemical properties and photocatalytic performance of the obtained catalysts. The mainresearch contents are as follows.(1) CaTiO3, SrTiO3, BaTiO3were synthesized by the coprecipitation method.The abilities of three catalysts to degrade methyl orange were compared. The resultdemonstrated that CaTiO3performed the best photocatalytic activity under theirradiation of simulated solar light. Subsequently, we explored the optimal calcinationtemperature and time for synthesizing the CaTiO3with good photocatalyticperformance. The electrochemical properties and photocorrosion inhibitionperformance of the obtained CaTiO3were also evaluated. The results showed thatCaTiO3with excellent photocatalytic performance and good crystallinity wasobtained after being calcined at700℃for5h. When the concentration of catalystwas0.1g·dm3, the degradation rate of methyl orange solution (10mg·dm3) reached90.36%in80min under the irradiation of simulated solar light. However, thephotocurrent density of CaTiO3weakened gradually as time went on and thus causedthe decrease of photocatalysis performance with increasing reaction times. Thecatalyst was partially decomposed into TiO2after reaction.(2) The rodlike CaTiO3was synthesized using template method. The calcinationparameters concluded in last chapter were applied in this chapter. The band gap ofas-prepared rodlike CaTiO3was narrowed. The influences of the concentration ofcatalyst and methyl orange on the degradation rate were investigated. The rodlikeCaTiO3exhibited enhanced performance in the photocatalysis, photocurrent density and photocorrosion inhibition test. When the concentration of catalyst was0.3g·dm3,the degradation rate of methyl orange was twice as much as the grainy one prepared inthe last chapter. What’s more, the signal was steady as time went on. In the recycleexperiment, the photocatalytic activity weakened slowly with increasing reactiontimes, which indicated that the photocorrosion inhibition of rodlike CaTiO3wasenhanced. During the reaction process, the rodlike CaTiO3turned into cubic structure,the crystal didn’t decompose but transform into CaTi4O9.(3) CaZrxTi1-xO3(x=0.00,0.02,0.05,0.08) were synthesized by coprecipitationmethod. The influence of calcinations temperature heating rate and Zr doping contentwere investigated. The results demonstrated that the catalysts exhibited excellentphotocatalytic performance when calcinated at850℃for3h at the heating rate of3℃/min. When the Zr content was0.05, the photocurrent density was13times asmuch as CaTiO3and the degradation rate of methyl orange reached91.44%in30min,which was2.5times as much as CaTiO3. Nevertheless, CaZr0.05Ti0.95O3exhibitedrelatively worse photocorrosion inhibition. The photodegradation rate of methylorange decreased rapidly with increasing times. The catalysts showed goodcrystallinity after reaction, but the diffraction peaks shifted to high angles, indicatingthat the Zr escaped from the bulk lattice to the surface and formed the recombinationcenters for the electrons and holes, and thus resulting in the reduction ofphotocatalytic activity.