Preparation And Properties Of Ag₃PO₄ Based Composite Photocatalysts

Silver phosphate?Ag₃PO₄?is a kind of visible light response of photocatalyst,and Ag₃PO₄ has a very high photocatalytic activity.Its quantum yield is as high as 90%.In recent years,research on Ag₃PO₄ photocatalyst has become a hot topic.Ag₃PO₄ has the advantages of low toxicity,high photocatalytic activity and high quantum yield,and it is the ideal catalytic material in the field of photocatalysis.At present,the studies of Ag₃PO₄ are mainly decomposition of water to hydrogen and photocatalytic degradation of organic pollutants such as methyl orange,methylene blue,phenol and bisphenol A,and photodegradation of isopropanol in the gas phase under visible light.However,Ag₃PO₄ also has the disadvantages of slightly soluble in aqueous solution,light corrosion,poor stability and other shortcomings,affecting its industrial applications.Therefore,how to improve the photocatalytic performance of Ag₃PO₄ is the focus of its modification research,so that it has high photocatalytic activity,and high photocatalytic stability.This paper around silver phosphate visible light photocatalyst,By Ag₃PO₄ photocatalytic material respectively with AgI and nitrogen doped carbonquantum dots?NCQDs?were prepared composite photocatalytic materials to improve the photocatalytic activity and stability of Ag₃PO₄ based composite materials.The relationship between the microstructure,the composition of heterojunction and the photocatalytic performance of the composites was revealed by photocatalytic experiments and various characterization methods,and the corresponding photocatalytic mechanism was proposed.The specific research contents are as follows:?1?AgI/Ag₃PO₄ composite photocatalytic materials were prepared by ion exchange method,and excellent photocatalytic activity was exhibited in photocatalytic degradation experiments.Among them,30%-AgI/Ag₃PO₄ photocatalyst showed the highest photocatalytic activity.After degradation of visible light for 35 min,the degradation efficiency of methyl orange was 95.1%,and its photocatalytic stability was also improved.According to the capture agent experiment,we can conclude that the active species of 30%-AgI/Ag₃PO₄ in the photocatalytic degradation process are mainly hole?h⁺?and superoxide radical?·O₂^??,in which the role of the hole is the largest,more than the role of oxygen free radicals.?2?The nitrogen-doped carbon dots were prepared by hydrothermal method at 180? for 11 h,then NCQDs/Ag₃PO₄ composite photocatalyst was prepared by precipitation method.In the photocatalytic experiment of degradation of methyl orange,under the visible light for 18 min,the degradation efficiency was as high as 98%,which showed high photocatalytic activity and stability.According to the capture agent experiment,we can conclude that the active species of NCQDs/Ag₃PO₄ during photocatalytic degradation are mainly hole?h⁺?and superoxide radical?·O₂^??,in which the hole plays the most role in photocatalytic degradation,followed by oxygen free radicals.?3?According to the capture agent experiment and the characterization of the catalyst materials,it is presumed that the photocatalytic mechanism of AgI/Ag₃PO₄ is that Ag₃PO₄ and Ag I form heterojunction,and the photoelectron on the AgI conduction band is transferred to the conduction band of Ag₃PO₄.The holes are transferred to the valence band of AgI,which promotes the separation of photogenerated electron holes and improves their photocatalytic activity and stability.The reason for the good photocatalytic performance of NCQDs/Ag₃PO₄ is that the introduction of NCQDs enhances the light absorption of Ag₃PO₄.Because NCQDs/Ag₃PO₄ composite photocatalyst will produce elemental silver in the process of photocatalytic degradation,the electrons on the surface of Ag₃PO₄ are transferred through the vector of Ag₃PO₄? NCQDs ? Ag in the photocatalytic process,and the formation of the Schottky in the NCQDs/Ag₃PO₄ composite system,where the electric field improves the separation efficiency of electron holes,and improves the photocatalytic performance of the composites.