Synthesis And Photocatalytic Properties Of Znse And Its Composites

As a Ⅱ-Ⅵ semiconductor,ZnSe is considered to be a promising class of photocatalysts due to its high photocatalytic activity and environmental friendliness.Since the microstructure of ZnSe has a great influence on its photocatalytic properties,it is of great research value to control the morphology of ZnSe and its composites through structural design.Based on this,the ZnSe microspheres and their composites were prepared by hydrothermal method through the regulation of reducing agent,element doping and heterojunction,and their morphology,structure and optical properties were characterized.Finally,the photocatalytic properties of ZnSe and its composites were investigated by using methyl orange solution as the target degradant.The specific research content is as follows:1.Synthesis of ZnSe microspheres.Zn（NO₃）₂·6H₂O and Na₂SeO₃ were used as precursors,and ZnSe microsphere samples were successfully synthesized in 10ml N₂H₄·H₂O and 0.67M NaOH solution.The influence of key parameters（N₂H₄·H₂O content,NaOH concentration）on the structure,type,optical properties and photocatalytic properties were systematically studied.It was found that the N₂H₄·H₂O content and the concentration of NaOH have a great influence on the type and structure of the product.When the content of N₂H₄·H₂O is more than 10 ml,the product is ZnSe·N₂H₄.When N₂H₄.H₂O is less than 5 ml,the product is a mixture of ZnO and ZnSe.Under the condition of without adding N₂H₄·H₂O,the final product is pure ZnO material regardless of the presence or absence of Na₂SeO₃.ZnSe and ZnSe·N₂H₄ were used for photocatalytic degradation of methyl orange solution to test its photocatalytic performance.The results show that the photocatalytic performance of ZnSe·N₂ H₄ flower sphere is better than that of ZnSe microsphere.2.X（Ag,Mn）:ZnSe doping.X（Ag,Mn）:ZnSe samples were prepared by adding different types and proportions of doping sources during the synthesis of ZnSe microspheres.The influences of doping elements and their doping amount on the structure,optical and photocatalytic properties of the products were investigated.The results show that the same concentration of doping source can cause significant changes in the morphology,optical and photocatalytic properties of the composite.Ag doping causes the formation of a rod-like structure,while Mn:ZnSe maintains the original microspherical appearance of ZnSe.In addition,the band gap changes of the Mn:ZnSe and Ag:ZnSe samples were different.Mn²⁺doping causes a decrease in the band gap of the Mn:ZnSe material and Ag⁺doping causes an increase in the band gap of the Ag:ZnSe material.The photocatalytic performance results show that the photocatalytic performance of Ag:ZnSe is weaker than that of ZnSe,and the photocatalytic performance of Mn:ZnSe increases with the increase of Mn²⁺doping ratio.3.Synthesis of ZnO/ZnSe composite.The ZnO/ZnSe composite structure sample was synthesized by a two-step hydrothermal method.Firstly,ZnO was synthesized by using Zn（NO₃）₂·6H₂O and NaOH as precursors.Then Se powder was used as Se source and sodium borohydride（NaBH₄）was used as reducing agent ZnO to synthesize ZnSe nanospheres on the surface of ZnO rod structure.The composite ratio of ZnO/ZnSe materials under different alkaline conditions and the photocatalytic properties of composites were compared.The results show that when the solvent is composed of 25ml H₂O and 15ml NH₃·H₂O,the photocatalytic performance of the ZnO/ZnSe composite structure is the best,due to the large specific surface area of ZnO/ZnSe and dislocation band gap arrangement of ZnO and ZnSe,which is favorable for electron-hole transport.