Synthesis And Photocatalytic Performance Of Silver Phosphate Photocatalyst

Photocatalytic oxidation technology has a wide range of applications in environmental protection,new energy development and other fields.Ag₃PO₄ has been widely concerned owing to the advantages of high quantum yield,strong catalytic activity and so on.At the same time,there some factors limiting its promotion and application,like Easy reduction and lack of stability.In this paper,considering the advantages and disadvantages of Ag₃PO₄ material,Ag₃PO₄,AgBr/Ag₃PO₄ and TiO₂/Ag₃PO₄ composite photo-catalysts were successfully prepared by the way of morphological control and semiconductor compound.The physical and chemical properties of the crystal structure,material morphology,valence bond state and photocatalytic performance of the prepared samples were studied by various characterization methods.After that,Photocatalytic activity and reaction kinetics were evaluated using methylene blue as simulating pollutant.Moreover,reaction mechanism in catalytic process was explored.The main conclusions of the paper are as follows:?1?A cube-type silver phosphate?c-Ag₃PO₄?catalyst was prepared by silver-ammonia assisted method using AgNO₃ and Na₃PO₄ as raw materials and ammonia as adjuvant.And,the spherical silver phosphate?s-Ag₃PO₄?prepared by simple precipitation method was used as a contrast.It was found that the degradation rate of c-Ag₃PO₄ to methylene blue was 92.7%under 30 min visible light irradiation,and the degradation rate of c-Ag₃PO₄ after being used 5 cycles was around 80%,which both were much higher than that of s-Ag₃PO₄.The photocatalytic degradation kinetics of methylene blue by c-Ag₃PO₄ and s-Ag₃PO₄ were studied by linear fitting,and which was confirmed to conform to the Langmuir-Hinshelwood first-order kinetics model.Moreover,the catalytic degradation rate of c-Ag₃PO₄ sample was0.088min^-1 by linear fitting,which was higher than 0.051min^-1 of s-Ag₃PO₄ sample.So that,it is believed that the catalytic activity,degradation rate and stability can be effectively improved by regulating the morphology of Ag₃PO₄.The results of cover radical experiment showed that the main active groups of c-Ag₃PO₄ in the process of catalytic degradation of methylene blue were superoxide?·O₂^-?.?2?AgBr/Ag₃PO₄ composite catalyst was prepared by in situ ion exchange using AgNO₃ and Na₃PO₄ as raw materials with NaBr as Br source.A series of AgBr/Ag₃PO₄ with different AgBr mass ratios were prepared by controlling the addition of NaBr.The results of catalytic degradation show that the introduction of AgBr can improve the degradation rate and stability of methylene blue on the catalyst,which both were higher than c-Ag₃PO₄.AgBr/Ag₃PO₄ had the best catalytic activity when the mass ratio of AgBr to Ag₃PO₄ was 0.2,and the degradation rate of AgBr/Ag₃PO₄-0.2 was 96.37%,which was 31.25%higher than that of c-Ag₃PO₄.The photocatalytic degradation kinetics of methylene blue by c-Ag₃PO₄ and the series of AgBr/Ag₃PO₄ were studied by linear fitting,and which was confirmed to conform to the Langmuir-Hinshelwood first-order kinetics model.The catalytic degradation rate of AgBr/Ag₃PO₄-0.2 sample to methylene blue was the highest,which was 0.1053min^-1.The results of cover radical experiment showed that the main active groups of AgBr/Ag₃PO₄ in the process of catalytic degradation of methylene blue were superoxide?·O₂^-?and holes?h⁺?.?3?Ti?SO₄?₂ and NH₄F were used as raw materials to prepare TiO₂ hollow sphere by chemical induced self-transformation method.Based on that,a series of TiO₂/Ag₃PO₄ composite photo-catalysts were prepared by precipitation method controlling the addition of AgNO₃ and Na₃PO₄.The results of catalytic degradation show that the introduction of TiO₂ can improve the degradation rate and stability of methylene blue on the catalyst,which both were higher than c-Ag₃PO₄.TiO₂/Ag₃PO₄had the best catalytic activity when the mass ratio of TiO₂ to Ag₃PO₄ was 3%,and the degradation rate of TiO₂/Ag₃PO₄-3%was 96.03%,which was 93.81%after being used 5 cycles.The photocatalytic degradation kinetics of methylene blue by c-Ag₃PO₄and the series of TiO₂/Ag₃PO₄ were studied by linear fitting,and which was confirmed to conform to the Langmuir-Hinshelwood first-order kinetics model.The catalytic degradation rate of TiO₂/Ag₃PO₄-3%sample to methylene blue was the highest,which was 0.0856 min^-1.The results of cover radical experiment showed that three kinds of radical were all involved.However,the effect of·O₂^-is small and negligible.Radical of h⁺plays decisive role in the catalytic process while·OH plays a secondary one.