Research On Preparation And Photocatalytic Performances Of Multi-component Nanoscale TiO₂ Composite Photocatalysts

TiO₂ is widely utilized as photocatalyst in removal of pollutants in environmental protection resulting from its characteristics of stability,powerful oxidizing and reducing ability and environmental friendliness.However,the quick recombination of photogenerated charge carriers,limited light-response range and low adsorption capacity are the main bottlenecks that restrict its large-scale practical application.Herein,the objects of palygorskite supported were optimizing nanoparticles dispersion and provide large specific surface area.In addition,Ag deposited and coupled with suitable semiconductors was aimed at improving photogenerated charge carrier separation and broadened the light-response range of TiO₂ into visible light region.Meanwhile,the structure-effect relationship between phase composites,microstructure,optical absorption behaviors and photocatalytic activities of the materials was investigated.The photocatalysis mechanisms were further discussed.The specific research contents of this manuscript are as follows:?1?Ag-TiO₂/palygorskite composites were syntheized by introduced palygorskite support and noble Ag.The results indicated that Ag-TiO₂ nanoparticles with size of 12-15 nm were adequately anchored onto the surface of palygorskite,and the S_BET was 126.04 m²/g.Especially,the optimal sample?6.0AgTP?showed the highest photocatalytic activity,achieving 99.48%and 95.27%degradation efficiency after UV-vis or visible-light irradiation,respectively.The enhanced photocatalytic activity was ascribed to the synergetic effect of surface plasmon resonance of Ag and palygorskite support effects.?2?ZnFe₂O₄@TiO₂ core-shell structure composite photocatalysts were fabricated by a two-step method.The TiO₂ nanoparticles with size of 8-12 nm were coated onto the surface of ZnFe₂O₄,and forming unique core-shell structure.The S_BET of optimal sample was 73.72 m²/g,and obtaining 95.6%degradation efficiency for MB under visible light irradiation.The developed mesoporous structure,large specific surface area and strong visible light absorption are the main reasons for the high charge carrier separation and enhanced photocatalytic activity of the samples.?3?ZnO/ZnFe₂O₄ heterojunction photocatalysts were facilely prepared by a two-step approach.ZnO and ZnFe₂O₄ crystallites were self-assembled with each other to form the octahedral-like nanoparticles with developed mesoporous structure.The bandgap energy and S_BET of optimal sample was 2.38 eV and 11.58 m²/g,respectively,and achieving 82.7%degradation efficiency for MB under visible light irradiation.To analyse the support effects of palygorskite,the ratio of mineral support to photocatalysts in ZnO-ZnFe₂O₄/palygorskite composite photocatalysts was adjusted to explore the effects of crystallite size,particle size and micromorphology on photocatalytic activity.The results showed that the support effects of palygorskite are to reduce particle size of photocatalysts,inhibit nanopartilces agglomeration,provide large specific surface area,and enhance adsorption capacity.?4?The ZnO/ZnFe₂O₄@TiO₂ core-shell structure photocatalyst was facilely synthesized by solvothermal method,and the octahedral-like ZnO/ZnFe₂O₄nanoparticles were used as nucleation center.The results demonstrated that the TiO₂nanoparticles with average size of 10.38 nm were adequately coated onto the surface of ZnO/ZnFe₂O₄ cores.The S_BETET of sample was 106.87 m²/g,and obtaining 96.32%degradation efficiency for MB under visible light irradiation.The efficient photogenerated charge carrier separation and enhanced photocatalytic property of sample was ascribed to the synergetic effect of unique core-shell structure,developed mesoporous structure and strong light absorption characterisitic.