Research On Electrochemical And Electromagnetic Properties Of Two-dimensional Carbon Nanomaterials

Two-dimensional carbon nanomaterial?graphene?,with its unique structure,has a large specific surface area,excellent electrical conductivity,thermal conductivity and mechanical properties.Since its discovery,people have tried to apply graphene to many aspects,such as chemical sensors,supercapacitors,lithium-ion batteries,and so on.In the paper,the vertical graphene is the main research object.Through material preparation and characterization,the material properties were studied from two aspects of electrochemical and electromagnetic properties,and its potential applications in the detection of trace heavy metal ions and millimeter wave fields were explored.The main research contents are as follows:1.Plasma enhanced chemical vapor deposition?PECVD?was used to deposit vertical graphene on substrate of graphite carbon paper.The effects of various process parameters on the growth of vertical graphene were briefly discussed.It was characterized by scanning electron microscope?SEM?,energy spectroscopy?EDS?,and Raman spectrum.The SEM results show that the way the vertical graphene grows perpendicular to the substrate makes it have rich edges and a large surface.In the EDS spectrum,carbon accounts for 97.7%and oxygen accounts for 2.3%,which indicates that the vertical graphene prepared by PECVD contains only a small amount of oxygen element.Raman spectrum,I_D/I_G=0.71 indicates that the vertical graphene material has defects,which may be vacancy defects or impurity defects.To a certain extent I_2D/I_G=1.24 reflects that the graphene material has fewer layers,no graphene stacked,and its large specific surface area can be fully utilized.The surface contact angle is greater than 90°,indicating that the surface of the vertical graphene is hydrophobic.2.Graphite carbon paper deposited with vertical graphene was used as the working electrode,and its electrochemical characteristics were studied by electrochemical analysis method.A large range?-3V to 2V?cyclic voltammetry scan to find the potential window of vertical graphene is at least between-1V and 1V.Cyclic voltammetry in potassium ferricyanide solution showed that the peak-to-peak voltage difference of the vertical graphene electrode was smaller than that of the graphite carbon paper electrode,and the oxidation peak and reduction peak of the vertical graphene electrode were larger than the graphite carbon paper electrode.Anode stripping voltammetry was used to detect heavy metal ions(Pb²⁺,Cu²⁺).As a result,the stripping potential of Pb ions was-0.56V,the linear range was at least 50-100ppb,and the detection limit was 1.48ppb.The stripping potential of Cu ions-0.04V.There is a shoulder peak around 0.137V,the linear range is at least 50-300ppb,and the detection limit is 5.64ppb.3.Through the combination of electromagnetic simulation and experimental testing,a method for testing the electromagnetic properties of materials in the millimeter wave band was initially proposed,and the following conclusions were drawn.In the frequency band of 90GHz-95GHz,by comparing the S₂₁ parameter curves of the silicon wafer with the S₂₁ curves of the silicon wafer sample with vertical graphene film deposited on the surface,it was found that the vertical graphene film coating can significantly change the electromagnetic wave transmission characteristics in the silicon wafer.In this frequency range,the absorption rate of the vertical graphene to electromagnetic waves is not good.