Electrochemical Preparation Of Graphene And Graphene Derivatives And Their Properties Research

Graphene(Gr)has attracted a lot of attention due to its superior electrical properties,thermal properties,optical properties and mechanical properties.Since its discovery,it has shown great application potential in many fields.In oLVSr to realize the research of Gr in many fields,it is first necessary to study the preparation method of Gr.Gr is mainly obtained by a chemical vapor deposition method,a ball milling method,and a redox method.However,these preparation methods always have problems of high cost,energy consumption,time-consuming,non-green or unsafe.It can be seen that the preparation of Gr by electrochemical method is more popular.However,this method has the disadvantages of low yield,large defects,small chip size and thickness of the sheet,which is the bottleneck problem of electrochemical preparation of Gr.Graphene derivatives,graphene oxide(GO),have excellent water solubility due to the presence of oxygen-containing functional groups on the surface and edges.It is not only using as a precursor for the preparation of Gr,but also can be used to prepare conductive films,carbon paper,fibers,gels,multifunctional separation membranes and other various composite materials.At the same time,due to the simultaneous presence of sp2 and sp3 hybrid carbon atoms,the controllable regulation of the band gap can be achieved by adjusting the ratio of the two hybrid carbon atoms.These excellent properties endow GO widely used in energy,environment,analysis,sensing,medical diagnosis and medical treatment.Liking as Gr,GO also has important significance in scientific research.At present,GO is mainly obtained by the Hummers method,but it is time-consuming,not environmentally-friendly,unsafe to operate,and requires a large amount of water for purification.Another derivative of Gr,graphene halide,can significantly change the electronic properties of Gr(promoting the opening of the band gap),electrochemical properties(increased reactivity)and chemical properties to meet the need for Gr used in various research fields.At the same time,the halogenated graphene,due to the strong electronegativity of the halogen,is advantageous for improving the positive charge of the C atom connected to itself and promoting the electrochemical activity,which makes ti widely research in the fields of fuel cells,lithium ion batteries,etc.At present,chlorinated graphene(Gr-Cl),which is mainly prepared by ultraviolet light or plasma treatment in a chlorine-containing atmosphere during ball milling,these methods are difficult to obtain Gr-Cl with low layer number and large area.In addition,these methods endanger the environment and human themselves.In view of the above problems,the main innovations of this paper are as follows:1.First,we experimentally confirmed that there are three processes of ion intercalation,graphite cutting and graphite flake(graphene)dispersion during the electrochemical preparation of Gr.On this basis,we propose a method of programmed electrochemical preparation of Gr by improving the intercalation efficiency of ions on the graphite layer,relieving the process of severely surface tailoring of graphite layer by hydroxyl radicals and promoting the dispersion of the graphite flakes to obtain yield,large area and thin layer of Gr.The method was very suitable for electro-exfoliation of industrial grade graphite rod to obtain single layer of Gr.What's more,the problem of coexistence of Gr and carbon microspheres(unpeeled carbon residue)produced during the process of electrolytic carbon rod could solved effectively,further to improve the quality of obtained Gr.2.Based on the programmed electrochemical preparation of Gr,we first proposed an electrochemical method for preparing deeply oxidized GO by increasing the effective concentration of·OH in aqueous solution,completely eliminating the use of concentrated sulfuric acid.Meanwhile,a large amount of GO could be obtained by continuously adding oxalic acid.By increasing the effective concentration of·OH in an aqueous solution,deep oxidation of Gr was achieved with an average lateral size is 1.5 ?m and the single layer of GO of was above 90%.We found that oxygen-containing free radicals could been produced under illumination of oxalic acid solutions,which further promotes the oxidation of GO.Benefit from a weak interaction between the aniline molecule and the GO,the swelling problem of the GO film in the process of sieving the salt was reduced,thereby enhance the salt rejection rate.3.Considering the short-lived factor of ·OH in aqueous solution,we proposed a method for rapidly preparing of GO at gram level in organic solvents.The average lateral size of GO was 1.5 ?m and the single-layer GO was above 95%.Our invented method could realize the controllable preparation of GO with different oxidation degree and we have found that adding a small amount of water during the preparation of GO was beneficial to increase the degree of oxidation.The highest oxidation degree was close to the GO prepared by Hummers method.The GO synthesized by us was suitable for the preparation of three-dimensional structure of Gr.And the excellent charge and discharge performance of supercapacitors was demonstrated.4.For the first time,we had developed an electrochemical in-situ chlorine functionalized graphene method.The obtained GrCl with smaller number of layers was functionally equivalent to others' methods.By this method,we could obtain different degrees of chlorine doped GrCl.The results shown that the Cl atoms were uniformly grafted on GrCl,and the active sites were covered with the entire GrCl region.The oxygen reduction test indicated that the prepared GrCl had superior catalytic performance and catalytic lifetime.