Fabrication And Photocatalytic Performances Of Silver Halide/ZnFe₂O₄ Composites

In recent yeas,semiconductor photocatalysis,as a high efficient environmental pollution control technology,has received extensive attention from researchers.Among them,the design and preparation of photocatalysts with visible light response,high quantum efficiency and high stability have always been the core issues of photocatalytic technology.Silver halide has become one of the research topics in the field of photocatalysis because of its outstanding performance in photocatalytic degradation of environmental pollutants and bacteria disinfection.However,a single silver halide material has the disadvantages of weak visible light response,poor stability,and easy recombination of photoelectrons and holes,which seriously hinders its practical application in the field of photocatalysis.Therefore,choosing a semiconductor with a suitable energy level structure combined with a silver halide to form composites caould effectively enhance its visible light absorption range and stability,and further expand the application of photocatalytic degradation of organic pollutants and sterilization.The spinel-type ZnFe₂O₄ nanomaterial is considered to be a new type of photocatalytic material with great application potential because of its narrow band gap,strong visible light absorption ability and photochemical stability.In this dissertation,combining the advantages of silver halide and ZnFe₂O₄,a one-step hydrothermal method was used to construct a silver halide/ZnFe₂O₄ composite system.A new type of composites with high efficiency and stability was obtained.A series of characterization and testing methods were used to study its microstructure and photoelectric properties and photocatalytic activity.At the same time,the mechanism of its photocatalytic performance enhancement was also studied and explored.The specific research contents were as follows:1.ZnFe₂O₄ nanoparticles were synthesized by sol-gel method,and Ag/AgCl/ZnFe₂O₄ composites with different ZnFe₂O₄ loadings were prepared by hydrothermal method.Using XRD,SEM,XPS,DRS and other characterization methods to analyze the microstructure,morphology and photoelectric properties.The composite material was examined for the degradation of rhodamine B?RhB?and its antibacterial activity against E.coli under visible light.The results showed that 1wt%Ag/AgCl/ZnFe₂O₄ had the best degradation performance for RhB,and completely degraded RhB at 70 min.When the content of ZnFe₂O₄ was increased to 10wt%,the degradation of bisphenol A?BPA?and the killing of E.coli were best.The results showed that the introduction of ZnFe₂O₄ and the surface plasmon resonance effect of Ag promote the separation and transfer of electron-hole pairs,and further enhanced their photocatalytic properties.2.Using synthesized ZnFe₂O₄ as raw material,Ag/AgBr/ZnFe₂O₄ composites were prepared by one-step hydrothermal method.The composition,morphology,and photoelectric properties of the composites were characterized by a variety of methods,and the successful preparation of the composites was confirmed.The results of visible light photocatalytic tests on E.coli and methyl orange?MO?showed that the composites exhibited better photocatalytic bactericidal and degradation than the single Ag/AgBr and ZnFe₂O₄.Among them,Ag/AgBr/ZnFe₂O₄-5wt%composites had the highest photocatalytic activity,and all bacteria were killed within 120 min under visible light,and the degradation efficiency of MO reached about 93.2%at 6 min.The experimental results showed that the introduction of ZnFe₂O₄ broaden the visible light response range of Ag/AgBr materials,which enabled effective separation of photogenerated electrons and holes,resulting in more active species,which was beneficial to the improvement of photocatalytic performance.3.Using ZnFe₂O₄ as raw material,AgI/ZnFe₂O₄composites were synthesized by hydrothermal method to achieve uniform distribution of ZnFe₂O₄ nanoparticles on AgI surface.The microstructure,morphology and photoelectric properties of AgI/ZnFe₂O₄ composites were analyzed by a variety of characterization methods.The photocatalytic activity of E.coli and rhodamine B?RhB?in the visible light was further investigated.It was found that when the loading of ZnFe₂O₄ was 5wt%,the AgI/ZnFe₂O₄-5wt%composite had the best performance and could kill all E.coli within 80 minutes of light irradiation,and the degradation efficiency of RhB was 98.5%at 40 min.The results showed that the combination of ZnFe₂O₄ and AgI could effectively improve the absorption range and stability of AgI in the visible region.The matching energy level structure between ZnFe₂O₄ and AgI was helpful to enhance the separation efficiency of photoelectron-hole pairs,which eventually made AgI/ZnFe₂O₄ composites have stronger visible light photocatalytic degradation and bactericidal activities.