Preparation And Modification Of FeVO₄ Photocatalysts

With the explosion of population and industrial development,a mass of organic pollutants have been released into natural waters,which has caused serious pollution problems to the quality of water.How to provide humans with clean water resources to meet the needs of production and life is a huge challenge for the society in the 21st century.Photocatalytic materials and technologies,as promising scientific solutions,can convert solar power into chemical energy for organic pollutant degradation.However,traditional photocatalytic material,such as TiO2,could only absorb ultraviolet light,which limits the utilization of sunlight.In order to improve the utilization of sunlight,photocatalytic materials with visible-light response have become a research hotspot.In this paper,a new visible-light response semiconductor such as FeVO4 has been fabricated.To solve the problem of practical FeVO4 with low specific surface area and high carriers recombination rate,FeVO4 has been modified in three ways,including FeVO4 nanonization,noble metal loading and nano-heterojunction construction,which have improved the visible light photocatalytic performance of the material system.The main contents and conclusions of this paper are as follows:(1)Nano-FeVO4 was prepared by solvothermal method.The effects of different weight ratios of ethylene glycol and water on the morphology and the photocatalytic activities of the samples were investigated.The structure and morphology of the samples were characterized by XRD,SEM,FT-IR and BET.The photocatalytic activity of the samples was evaluated by the degradation reaction of methylene blue under visible light(>400 nm).The photocatalytic principle of nano-FeVO4 was analyzed by PL,Zeta potential,DRS and other tests.The results implied that the particle size and band gap of FeVO4 nanoparticles declined first and then increased,with the increasing amount of ethylene glycol.When the weight ratio of ethylene glycol to water was 1:1,the prepared nano-FeVO4 showed largest specific surface area(22.057 m2/g)and narrowest band gap(1.97 eV).The highest value of the first order reaction rate constant k for nano-FeVO4 towards methylene blue could reach 0.23h-1.(2)Ag nanoparticles were loaded on the surface of nano-FeVO4 through photoreduction,thus obtaining a photocatalytic composite material.XRD,SEM,TEM,XPS and other research methods were used to characterize the morphology of the sample.The photocatalytic activities of the sample were tested by the degradation reaction of Rhodamine B under visible light(>400nm).The photocatalytic theory of Ag-loaded FeVO4 was analyzed by PL,DRS and other tests.The results showed that the amount of Ag+,the illumination time and the addition of the hole trapping agent methanol have effects on the yield of Ag nanoparticles and thus affect the material properties.The Ag nanoparticles generated by the photoreduction method were homogeneously dispersed on the surface of FeVO4 nanoparticles.The Schottky barrier formed between the metal Ag and FeVO4 is beneficial to the transfer of photogenerated electrons by improving the photocarrier separation rate.In addition,the Ag nanoparticles could improve the visible light photocatalytic activity of the system by introducing the plasmon resonance effect,which could increase the utilization of visible light.With the increased loading of Ag nanoparticles,the photocatalytic activities of silver-loaded FeVO4 composite photocatalysts increased first and then decreased.The highest value of the first order reaction rate constant k for the decomposition towards rhodamine B reached 0.076h-1,1.9 times higher than that of the nano-FeVO4.(3)AgC1 nanoparticles were firstly loaded on the surface of nano-FeVO4 by precipitation,and then Ag/AgCl/FeVO4 were prepared by photoreduction,in which process some nano-Ag were produced from AgCl in situ.XRD.SEM,TEM,XPS and other research methods were used to characterize the morphology of the samples.The photocatalytic performance of the sample was evaluated by the degradation reaction of Rhodamine B under visible light(>400nm).The photocatalytic principle of Ag/AgCl/FeVO4 was researched by PL,DRS and other tests.The results showed that the content of AgCl,the source of Cl-and the time of photoreduction had great influences on the morphology and properties of the composite samples.The visible light photocatalytic activities of Ag/AgCl/FeVO4 stengthed first and then weakened with the increase of photoreduced time.The highest value of the first order reaction rate constant k for the decomposition towards rhodamine B was 0.33h-1,which wass 2.06 and 8.25 times higher than that of AgCl/FeVO4 and nano-FeVO4.