Studies On The Liquid-phase Exfoliation Of Few Layer Tin Selenide And Its Catalytic Performances

Tin selenide(Sn Se)is a common layered semiconductor material,which has adjustable band gap,high photosensitivity and fast photo-response characteristics.These unique properties make it show wide application prospects in the fields of field effect transistors,photocatalysts,solar cells,photovoltaic materials and so on.However,the lack of large-scale preparation of Sn Se nanosheets hinders their development and utilization.Among the existing preparation methods,the liquid phase exfoliation method is one of the feasible methods for large-scale production of two-dimensional nanosheets.However,at present,the liquid phase exfoliation of Sn Se nanosheets encounters low exfoliation yield and the use of toxic organic solvents.Therefore,the development of an efficient and green exfoliation method for Sn Se nanosheets has become a key issue to be urgently solved.In this work,three exfoliation systems including organic salt-DMSO,amino acid aqueous solution and polyphenol aqueous solution are developed and are applied in the liquid phase exfoliation of Sn Se nanosheets.The few-layer Sn Se nanosheets with high-yield are obtained.The main contents are as follows:1.Sn Se nanosheets are prepared in DMSO with the assist of different intercalation agents(sodium citrate,sodium tartrate and sodium oxalate)by liquid-phase ultrasonic exfoliation method.The exfoliation yield can reach as high as 28.3%.Compared with neat DMSO,the addition of intercalation agent significantly improves the exfoliation yield of Sn Se nanosheets in DMSO.Through a series of characterization for nanosheets,such as TEM,SEM,XRD and AFM,it is found that the layers number of as-prepared Sn Se nanosheets is main 1-5.Mechanism studies have shown that organic salt can enter the interlayers of Sn Se,which results in the interlayer distance becoming larger and thus the exfoliation efficiency is improved.The prepared Sn Se nanosheets were used as photocatalysts to photodegrade organic dyes(methylene blue,rhodamine).The results shows that compared with bulk Sn Se,the photodegradation rate of Sn Se nanosheets for organic dyes is greatly improved.After 5 cycles,the highcatalytic activity is remanined.2.The eight kinds of amino acid aqueous solutions are used to exfoliate the bulk Sn Se to Sn Se nanosheets by liquid-phase ultrasonic exfoliation method,and the exfoliation yield was as high as 19.4%.The exfoliation yield is closely related to the hydrophilicity and hydrophobicity of amino acids and its chain length.Through the characterization of Sn Se nanosheets,most of Sn Se nanosheets with 2-8 layers are found.In addition,as-prepared Sn Se nanosheets are used as electrocatalysts in the hydrogen evolution reaction.The experimental results show that Sn Se nanosheets have high catalytic activity,good durability and high stability due to the more exposed active sites and larger specific surface area of Sn Se nanosheets.3.Four kind of green polyphenol aqueous solutions(tannic acid,gallic acid,epicatechol,chlorogenic acid.)have been developed and used for the liquid phase exfoliation of Sn Se nanosheets,with a exfoliation yield as high as 26.4%.By the study on the exfoliation mechanism,it is found that the efficiency of exfoliation Sn Se is related to the number of pyrogallol and catechol groups in the polyphenol.Through the characterization of Sn Se nanosheets,it is found that Sn Se nanosheets retain the complete crystal structure,and the thickness of 80% Sn Se nanosheets is less than 4 nm.The photocatalytic performance of Sn Se nanosheets is evaluated through the photocatalytic water splitting reaction.The results show that hydrogen production rate of Sn Se nanosheets is 2.3 times higher than the bulk Sn Se,indicating that Sn Se nanosheets have higher catalytic activity.