Preparation And Application Of Nitrogen-doped Graphene-Based Composites

As a special nanomaterial,graphene has many characteristics such as high electrical conductivity and high thermal conductivity,which provide the basis for its application in the fields of catalysis,energy storage and thermal management.However,the unique thin two-dimensional structure of graphene makes it easy to agglomerate in actual use.Make full use of the excellent properties of graphene.The three-dimensional graphene aerogel formed by the reduction and self-assembly of graphene oxide can give its composite material more excellent electrical and thermal conductivity.In this thesis,self-made graphene oxide is used as the raw material,and the three-dimensional structure of nitrogen-doped graphene aerogel is prepared by the "one-pot hydrothermal method",and it is systematically studied as a functional conductive carbon carrier to support Pt and thermally conductive filler to wrap at low temperature Phase change alloy composite materials,and discuss the effect of nitrogen doping amount and type on the catalytic activity and thermal conductivity of the composite materials.The main research contents and results are summarized as follows:Research the "one-pot hydrothermal method" nitrogen-doped graphene aerogel(NGA)preparation method.Using graphene oxide as raw material and urea as reducing agent or nitrogen dopant,under milder experimental conditions,graphene aerogels with higher nitrogen doping content were successfully synthesized.Using SEM,TEM,XRD,FTIR,XPS and other test methods to characterize the morphology,structure and composition of the material,it shows that urea can effectively chemically reduce graphene oxide and dope with nitrogen in one step under hydrothermal conditions.The optimal reaction conditions were screened out,and finally the highest nitrogen doping amount of NGA was 10.63 at%.The main nitrogen doping types were pyridine nitrogen and pyrrole nitrogen,and pyrrole nitrogen accounted for 4.79 at%.In addition,the NGA synthesized by this method has a rich porous structure.To study the transformation of NGA nitrogen-doped type and the method of carrying Pt on this carbon carrier.Using high-temperature sintering treatment,Pt is supported by the ethylene glycol reduction and reflux method,and the pyridine nitrogen-type nitrogen-doped graphene aerogel supported platinum catalyst(Pt/NGA)is obtained.After high temperature sintering,the nitrogen-doped type changes from pyrrole nitrogen to pyridine nitrogen,and the NGA pyridine nitrogen content sintered at 850? is as high as 5.14 at%.The Pt/NGA catalyst prepared by using this as a carbon support,the Pt particle size is 2.1?2.4 nm,and the Pt/NGA-850 catalyst with the most pyridine nitrogen content shows the best catalytic activity.The half-peak potential and the mass specific activity are respectively It is 0.814 V and 170.91 mA/mgPt,and the oxygen reduction reaction process is mainly carried out by the four-electron transfer pathway.It is proved that the type of pyridine nitrogen doped with nitrogen helps to improve the catalytic activity of Pt/NGA catalyst.Nitrogen-doped graphene aerogel/foam metal/low-temperature phase change alloy composite materials with high thermal conductivity were prepared,and the nitrogen-doped graphene aerogel,foamed nickel,foamed copper,and nitrogen-doped graphene coated foamed copper,etc.The framework composite low-temperature phase change alloy is used as a comparative analysis to characterize the phase change latent heat,melting point,thermal conductivity,thermal diffusivity and constant pressure specific heat capacity of the composite material.Studies have found that the introduction of the framework will reduce the latent heat of phase change of the composite material,but will not cause the alloy melting point to change,and the thermal conductivity of the composite material will be improved.The most significant improvement at 25? is:the nitrogen-doped graphene aerogel framework is 205.6%,the foamed copper skeleton is 186.8%,and the nitrogen-doped graphene-coated foamed copper skeleton is 209.6%.It shows that nitrogen-doped graphene does not negatively affect the thermal performance of the composite material,but it provides high thermal conductivity due to the provision of lone pairs of electrons.