Study On The Fabrication And Modification Of Meso-Macroporous Strontium Titanate Thin Films

Strontium titanate?SrTiO3?porous film has received extensive attention in the fields of photocatalysis and adsorption due to its advantages such as large specific surface area,low cost and recyclability.However,there are still problems in low utilization of visible light and easy recombination of photocarrier,leading to reduction of photocatalytic activity.Hierarchically pore structure can improve the loading capacity and facilitate the micro-scale transmission of ions and electrons,while the light absorption of SrTiO3 can be extended to the visible light region by doping modification.Therefore,it is of great theoretical significance and practical application value to explore the preparation of hierarchically pore structure SrTiO3 porous films and their doping modification.In this dissertation,meso-macroporous SrTiO₃ thin film was prepared by sol-gel immersion pulling method using tetrabutyl titanate as a titanium source,strontium acetate as a strontium source,diethanolamine?DEA?as a complexing agent,and PEG 2000 as a templating agent.Then,the effect of cerium?Ce?doping on their photocatalytic performance was studied.Rhodamine B?RhB?and methylene blue?MB?were used as simulated pollutants to conduct photocatalytic experiments.The influence of main technological parameters on the microstructure and phase composition of the as-synthesized products was studied,and the internal relationship between the corresponding microstructure and photocatalytic performance were also discussed.?1?The DEA:Sr:Ti molar ratio increased from 4:1:1 to 4.5:1:1,SrTiO3 porous film with different pore structure characteristics from bicontinuous mesoporous-macroporous structure to irregular mesoporous-macroporous structure after an ordered distribution transition.The corresponding band gap values changed from 2.19 eV,3.05 eV to 2.3 eV,2.95 eV.?2?Under the optimized conditions?sol concentration 0.3 mol/L,the molar ratio of DEA:Sr:Ti 4:1:1,the molar ratio of H₂O:Sr:Ti 45:1:1,the addition amount of PEG 2000 1.2g/100 mL,calcinated at 800^°C for 3 h?,the hierarchically pore structure SrTiO₃ porous film constructed by overlapped particles possessed both macropores?80-400 nm?and mesopores?1-10 nm?was prepared,the specific surface area of which achieves 12.9 m²/g.The degradation efficiency of RhB reached 99.8%after 500 W mercury lamp irradiation for 90 min.The formation of macropores in the as-synthesized meso-macroporous structure SrTiO₃ film was related to the phase separation caused by the difference in polarity between the polymer phase and the solvent phase,and the formation of mesopores was related to the oxidation and decomposition of organic substances during the calcination process.?3?The optimum modification process conditions were determined as follows:the doping amount of Ce was 20 at%,the molar ratio of H₂O:Ti was 45:1,the molar ratio of DEA:Ti was 4:1,the addition amount of PEG 2000 was 1.2 g/100 m L,and the calcination was carried out at800^°C for 3 h.The as-prepared Ce doped nanocrystalline SrTiO₃ porous film sample had a specific surface area up to 176.58 m²/g.The degradation efficiency of MB reached 86.25%after500 W mercury lamp irradiation for 90 min,which was 20.6%higher than that of undoped SrTiO₃ porous film.The band gap value of doped film was reduced by 1.38 eV compared with that of undoped film.