Study On Top-Down Synthesis Of Antimonene And Its Regulation Of Ion Transport Properties

Due to the advantages of high surface energy,large specific surface area,and good flexibility,two-dimensional materials have been extensively studied in the fields of optics,magnetism,thermotic,and energy conversion.As a kind of layered semi-metallic material,antimonene shows a lower ion transport energy barrier theoretically owing to its unique structure and composition.Therefore,in recent years,antimonene has gradually become one of the research hotspots of electrode materials for secondary batteries and capacitors.However,?-phase antimony,as the bulk material of antimonene,has small interlayer spacing and strong interlayer interaction,leading to small size and a large number of layers of antimonene obtained by traditional two-dimensional material synthesis methods,such as liquid phase exfoliation,electrochemical intercalation,and lithium ion intercalation,thus failing to achieve high-efficiency ion transport characteristics.Given these problems,this dissertation developed a series of new"top-down"synthesis methods to prepare large-size,few-layer,and high-quality two-dimensional antimonene.We systematically studied the influence of dimensions,size and surface composition of antimonene on its ion transmission performance and successfully applied it in energy and environment-related devices such as lithium ion batteries and capacitive deionization cells.We believe the results here provide important guidelines for the controllable preparation and industrial application of antimonene in the future.The main research results are as follows:(1)The traditional liquid phase exfoliation method was used to prepare antimonene and antimony quantum dots by adjusting the ultrasonic power.The performance of lithium ion battery of bulk antimony,antimonene,and antimony quantum dots was compared and analyzed from the perspective of lithium ion transport capacity.Among them,the average size of antimonene is about 600 nm,the thickness is 2-21 nm,and the average size of antimony quantum dots is about 24 nm.The?-phase bulk antimony exhibits very poor stability due to the fragmentation of the electrode stemming from volume expansion and contraction during the charge-discharge process.Antimonene and antimony quantum dots show excellent electrochemical properties.However,the performance of antimony quantum dots at high current density is inferior to that of antimonene.Theoretical studies show that the diffusion energy barrier of lithium ions in the in-plane direction(0.25 e V)is lower than that in the out-of-plane direction(1.14 e V),so the large transverse size of antimonene is more conducive to the transport of lithium ions.In-situ transmission electron microscopy(TEM)shows that the volume change of antimonene during sodium intercalation mainly arises from the in-plane volume expansion caused by the increase of the adjacent side angle.Antimonene can eliminate the harm caused by the volume change because of its special two-dimensional morphology.(2)Due to the problems of small size and large thickness of antimonene prepared by liquid phase exfoliation,a pressurized alloying approach for the preparation of large-size antimonene is proposed for the first time,and deep desalination is realized by antimonene in ultralow Na Cl concentration.The antimonene prepared by the pioneering"top-down"method,i.e.the pressurized alloying approach,has a lateral size of about 2-3?m,a thickness of less than 2nm,and a yield of up to 25%.The large-size and ultra-thin antimonene is very conducive to ion transmission,and the high yield meets the application requirements of antimonene in the energy field.Based on this,the diffusion energy barrier of sodium ions in the antimonene surface was calculated according to first-principles calculations,and the sodium ion transport capacity of antimonene with different sizes(antimonene prepared by pressurized alloying approach and liquid phase exfoliation)and bulk antimony was compared by the galvanostatic intermittent titration technique.Research on the capacitive deionization performance of large-size antimonene shows that its salt adsorption capacity reaches 20.62 mg·g^-1 without any treatment,which is comparable to traditional two-dimensional materials.(3)Given the inevitable oxidation in the antimonene synthesis process,hydrochloric acid was used to regulate the surface components of antimony to improve the ion transport capacity and increase the salt adsorption capacity to 31.4 mg·g^-1.In combination with other antimonene synthesis works and experimental experience,it is found that oxidation is inevitable in the process of antimonene synthesis.The presence of antimony oxide will weaken the electrical conductivity of antimonene and hinder the transport of ions in antimonene.In this work,antimonene is treated with hydrochloric acid to corrode the oxides on the surface of antimonene,thus improving the electrical conductivity.We also found that the hydrochloric acid treatment produces abundant pores on the surface of antimonene,that increases the specific surface area of antimonene.Also,hydrochloric acid treatment can improve the hydrophilicity of antimonene to some extent.The increase of electrical conductivity accelerates the ion transport rate of antimonene,the increase of specific surface area and the improvement of hydrophilicity increase the contact area between antimonene and the electrolyte,shortening the ion diffusion distance to improve the ion transport capacity of antimonene,and finally increase the salt adsorption capacity of antimonene by 53%.