Study On Preparation And Functional Properties Of Hybrid Graphene-based Materials With Magnetic Metal Compounds

With the development of modern science and technology,the application of electromagnetic waves has become more and more extensive,but the harm caused by electromagnetic waves has also increased.Facing the increasingly serious problem of electromagnetic pollution,designing an absorbing material with good characteristics such as light weight,thin thickness,strong absorption power,and absorption frequency bandwidth is the best way to solve this problem.Graphene itself has unique chemical properties such as light,heat,force,electricity,etc.,so it has received extensive attention from scientific researchers.However,the high conductivity of graphene itself will make its impedance matching performance relatively poor,causing a large number of reflections of electromagnetic waves on its surface.Therefore,pure graphene cannot meet the actual needs of absorbing materials.The introduction of magnetic particles into graphene can effectively improve the matching characteristics of graphene-based materials.At the same time,under the synergistic effect of the interface between graphene and magnetic particles and the magnetic loss of magnetic fillers,the microwave absorption performance is enhanced.This thesis takes graphene oxide sheets and graphene aerogels as the research objects,from the Si O₂ template for constructing graphene aerogels to the preparation of magnetic metal compounds@graphene-based aerogel hybrid materials,and graphene oxide Based on the preparation of hybrid materials,the microwave absorption properties and electrocatalytic properties of hybrid materials with several structures have been systematically studied.The specific work and research results of this paper are as follows:(1)Using Tetraethyl orthosilicate(TEOS)as the silicon source,Si O₂ aerogel was prepared by combining the sol-gel method and the atmospheric drying process;on this basis,the cationic surfactant hexadecane was added Trimethylammonium bromide(hexadecyltrimethylammonium bromide,CTAB)regulates the structure of aerogels.The effect of the addition of CTAB on the pore size of Si O₂ aerogel was studied.The experiment found that when the addition of CTAB was 0.0005 mol,the obtained aerogel formed better,with a specific surface area of 502.58 m²/g and an average pore size of 14.62 nm.The surface of the skeleton structure is relatively smooth.At the same time,based on the Si O₂aerogel template,the graphene aerogel was constructed by the CVD method,and the growth mechanism of the graphene aerogel was explored.Experiments have found that the Si O₂template structure has a significant impact on the structure of graphene aerogels.After CH₄is cracked,it is deposited on the template framework and assembled into graphene aerogels.The curved growth on the framework causes graphene aerogels to produce highly defective structures.(2)The bimetallic precursor(ferrocene hydrazone condensed nickel)is introduced into the graphene aerogel and GO system,and the magnetic metal compound@graphene-based hybrid material is obtained by high-temperature pyrolysis.The control mechanism of temperature and oxygen-containing groups on its growth and structure was explored,and it was found that the annealing temperature and GO oxygen-containing functional groups determine the structural composition of the hybrid material,which in turn can control the impedance matching characteristics of the hybrid material.In addition,the exploration of microwave absorption properties of magnetic metal compounds@graphene-based hybrid materials have been further expanded.Experiments have found that when the annealing temperature is 600°C,the graphene-based hybrid materials all exhibit good microwave absorption properties.Among them,when the thickness of the graphene aerogel hybrid material is 2.7 mm,its maximum effective absorption bandwidth is 7.08 GHz,and the minimum reflection loss(RL)value is-47.3 d B.The minimum reflection loss value of the graphene hybrid material is-40.3 d B at a frequency of 11 GHz,and the effective absorption bandwidth is 4.55 GHz(from 9.25 to 13.8 GHz).(3)Test the ORR/OER electrocatalytic performance of the hybrid material on the electrochemical workstation in the KOH alkaline system,systematically explore the relationship between the composition of the hybrid material,the structural difference and the electrocatalytic performance,and expand the hybrid material.The functional application of chemical materials in the field of electrocatalysis.Studies have found that graphene aerogel-based hybrid materials have relatively excellent electrocatalytic performance.In ORR,its initial potential,half-wave potential and limiting current density ratio are E₀=1.02 V,E_1/2=0.75 V,j_lim=4.9 m A/cm².In OER,because the system contains Fe materials with different valence states,the overpotential required to achieve a current density of 10m A·cm^-2 is the smallest,which is only 341 mV.