Preparation And Properties Of Silver-Based Vanadate Photocatalytic Materials

In recent years,energy depletion and environmental pollution restrict the development of society.Water pollution directly endangers human health and survival.The traditional sewage treatment technology has the disadvantages of high cost and low treatment efficiency,and there are still some difficulties in the practical treatment.Solar photocatalytic technology has the characteristics of high efficiency,environment friendly and so on.It provides an ideal method for scientific research workers to make use of energy and control environmental pollution.Among many photocatalytic materials,silver based photocatalyst has become a research hotspot because of its simple preparation process and high photocatalytic activity.Silver based vanadate,represented by AgVO3 and Ag3VO4 photocatalyst,is a kind of silver based photocatalytic material with high photocatalytic activity,mild conditions and mutual conversion.There are different forms of vanadate ions at different p H values,which can easily form photocatalytic materials with different phases.At the same time,the band gap of the silver vanadate is close and the band position is mismatched.Therefore,it has a good research prospect.In this paper,AgVO3,Ag3VO4 and three phase composite photocatalysts were prepared by adjusting the process parameters,and the band structure,micromorphology and photocatalytic activity of the photocatalyst were systematically studied.Ag3VO4 photocatalyst was prepared by liquid precipitation method.The XRD patterns showed that the sample had no impurity.SEM images showed that the p H value of the solution has a great influence on the morphology of the sample.When the p H value is 7,the morphology of the sample is the most uniform,the size of the sample is small and the size distribution is between 200-500 nm.UV-vis absorption spectra showed that all the samples prepared had visible light absorption properties.The Ag3VO4 photocatalyst prepared with the solution p H value of 7 has the best visible light photocatalytic activity,and the PL spectrum shows that the sample has the best photocatalytic carrier separation efficiency,which is one of the reasons for its best photocatalytic activity.In addition,the type and dosage of surfactants have a great influence on the reaction products.The samples prepared with 0.05 g PVP have the best photocatalytic activity.The AgVO3 photocatalyst with rod like morphology was prepared by hydrothermal method,and the Ag elemental was produced by Na BH4 solution in order to form a Ag/AgVO3 composite photocatalyst.No other vibration peaks in Raman spectra,combined with the XRD patterns proved that the experimental samples was pure phase AgVO3 photocatalyst.SEM images showed that the AgVO3 photocatalyst prepared at the reaction time of 12 h has the most complete rod structure and smooth surface.The Ag/AgVO3 composite photocatalyst has the most uniform morphology when the AgVO3 photocatalyst was reduced to 5%,and the sample also shows the best visible light photocatalytic activity.Ag3VO4/Ag/AgVO3 composite photocatalyst was prepared by the two step method.From the XRD patterns,it was proved that there were Ag3VO4,Ag and AgVO3 threephase in the reaction products,and there was no other phase.There are no different absorption bands in the UV-vis absorption spectra of Ag3VO4/Ag/AgVO3 composite photocatalyst because of the absorption edge of AgVO3 and Ag3VO4 is similar.When the ratio of Ag3VO4 to Ag/AgVO3 is 2:1,the prepared Ag3VO4/Ag/AgVO3 composite photocatalyst showed the best photocatalytic activity under visible light.The performance is 5.1 times and 19.2 times higher than that of the single Ag3VO4 photocatalyst and AgVO3 photocatalyst,respectively.In addition,the photocatalytic stability of the sample is also good.Through the band structure analysis and free radical capture experiments,it was found that the transfer behavior of photo generated carriers in Ag3VO4/Ag/AgVO3 composite photocatalyst is in line with the Z-scheme transfer mechanism.This is the reason why the photocatalytic activity and stability of the composite are improved.