Preparation Of Silver Phosphate-titanium Dioxide Composite Material And Its Photocatalytic Performance

In recent years,based on the needs of environmental protection,the research work on the synthesis of photocatalysts using semiconductor materials has yielded some important results.Among the many semiconductor materials,titanium dioxide(TiO2)and silver phosphate(Ag3PO4)have attracted much attention because of their enormous potential.However,titanium dioxide wide band gap of 3.2eV restricts its photocatalytic activity to the ultra violet region of spectrum low activity in visible light;powders are easily colloidal in solution and difficult to recycle.On the other hand,Ag3PO4 are physiochemically unstable and can be easily reduced to the Ag element,limiting its photocatalytic application.Therefore,to remove these defects of TiO2 and Ag3PO4 photocatalysts,Ag3PO4-TiO2 composites were prepared by in-situ precipitation method.In order to improve photocatalytic activity and stability of the catalyst,Ag3PO4-TiO2 was further modified by changing the morphology of the composite material,complexing with low water-soluble AgI,and ion doping.The specific research work is as follows:1.The TiO2 nanobelts(TNBs)were prepared by hydrothermal method.The effects of calcination temperature on the morphology,crystal structure and catalytic performance of Titania nanoribbons were studied.The photocatalytic tests showed that the nanoribbons obtained at the calcining temperature of 600?,have best photocatalytic activity.In situ precipitation method was used to load silver phosphate on the titania nanobelts(TNBs)surface to further improve the photocatalytic activity of the photocatalyst.The results show that the Ag3PO4-TNBs have double band gap structure.When the molar ratio Ag3PO4 to TNBs is 3:10,the photocatalytic activity and the stability of the catalyst is improved as compared with pure Ag3PO4 under simulated sunlight irradiation.The holes(h+)play a major role in the degradation of rhodamine B(RhB).2.In order to solve the poor cycling performance of Ag3PO4-TNBs composite catalyst,AgI-Ag3PO4/TNBs ternary composite catalysts were prepared by modifying Ag3PO4-TNBs with AgI by lower solubility product.Studies have been shown that when the AgI and the Ag3PO4 molar ratio is 3:5,then AgI-Ag3PO4/TNBs has the best photocatalytic activity.Compared to Ag3PO4-TNBs composite,AgI-Ag3P04/TNBs ternary composite catalyst maintains good activity after five cycles experiments,its degradation rate increased from 64.2%to 85.8%.Experiments confirmed that AgI can effectively inhibit the reduction reaction of Ag3P04 in the medium and improve the stability of ternary composite catalysts.Mechanism studies have shown that holes(h+)and superoxide(·O2-)radicals play a major role in the catalytic system.3.Three-dimensional titanium dioxide nanoflowers TiO2(3D)were prepared by hydrothermal method.The effect of reaction conditions on the morphology of TiO2(3D)was studied.The best catalyst morphology is obtained,when the hydrothermal reaction time is 14h and the solvents used are ethylene glycol.After calcination temperature at 600?,it is completely converted to an anatase phase and catalyst has an optimal catalytic activity.Ag3PO4(SO42')-TiO2(3D)three-dimensional composite was prepared through in-situ precipitation method.Ag3PO4 doped with sulfate was loaded on the surface of TiO2 nanoflowers,and the results show that Ti02(3D)plays an important role in controlling the particle size of Ag3PO4(SO42-).When the atomic ratio of sulfur in the composite catalyst is 0.59 at%,the degradation rate of rhodamine B can reach 99.1%in 20 min under visible light irradiation and the photocatalytic effect remained unaffected at 87.6%after 5 cycles.Mechanism studies indicate that holes(h+)play a major role in the degradation process.