Study On The Preparation Of Graphene Aerogel And Its Mechanical Performance And Adsorption Properties

Graphene aerogel?GA?is a three-dimensional porous material constructed by graphene sheets,which combines the advantages of graphene materials and aerogel materials.It not only exhibits good optical,electrical and thermal properties,but also has high porosity,high specific surface area and good compression resilience.The application of graphene aerogel in lithium ion batteries,supercapacitors,sensors,adsorption materials and other fields has attracted extensive attention.The good morphology,structure and mechanical properties of graphene aerogel are the key to ensure its application reliability.In this paper,GA was prepared by chemical reduction and self-assembly process using graphene oxide?GO?as precursor.The morphology and structure of the prepared GA were characterized by scanning electron microscope?SEM?,transmission electron microscope?TEM?,X-ray diffraction?XRD?,Fourier infrared spectroscopy?FT-IR?,X-ray photoelectron spectroscopy?XPS?and Raman spectroscopy?Raman?.Universal testing machine was used to test the compression resilience of GA.The pore size was characterized by N₂ adsorption and desorption,and its adsorption capacity for organic compounds was tested.The specific research content is as follows:?1?Experimental parameters will affect the morphology,structure and mechanical properties of GA.In this experiment,GA was prepared by chemical reduction method.The effects of the concentration of GO solution,the dosage of reducing agent EDA,reduction temperature and the reduction time on the morphology,structure and mechanical properties of graphene aerogel were studied.The results showed that the volume shrinkage of the hydrogel decreased with the increase of GO concentration.When the GO concentration was 3 mg/ml,the prepared graphene aerogel had low density,homogeneous microstructure and better mechanical properties.With the increase of EDA content,the compression modulus of graphene aerogel increased.When the volume ratio of GO solution to EDA was 250:1,the graphene aerogel with better pore diameter distribution and higher mechanical properties were obtained.GO can be reduced adequately at 95°C.The morphology of GA nearly unchanged after the reduction time was more than 6 h.Thus the optimization experimental condition are:GO solution concentration is 3 mg/ml;the volume ratio of GO solution to EDA is 250:1;the reduction temperature is 95°C and the reduction time is 6 h.?2?The graphene aerogel with ordered pore size was prepared by using n-hexane as soft template.The droplets of n-hexane could induce the orderly self-assembly of GO sheets.The prepared GA had regular spherical pores,which reduced the disorderly stacking of graphene sheets.When the volume ratio of n-hexane to GO solution was1:2,the prepared graphene aerogel had higher porosity?99.85%?and higher specific surface area?155.2 m²/g?than the aerogel without template.Therefore,n-hexane can play a role in regulating the pore size structure of GA.?3?Since TEOS molecules are prone to hydrolysis in water to generate silica alcohol?Si-?OH?₄?,it is speculated that TEOS can react with oxygen-containing functional groups on the surface of GO.Therefore,TEOS are introduced into GO solution to prepare SiO₂-enhanced graphene aerogel.Research results showed that the microstructure of GA can be regulated and the C-O-Si covalent bond can be produced between graphene sheets by the reaction of TEOS and GO,thus the mechanical properties of GA was improved.When the mass ratio of TEOS and GO powder is 3,TEOS-3 obtained the best mechanical properties?the compression modulus is 29kPa at the strain of 50%?,which is 20 kPa higher than pure GA.The aerogel of TEOS-3 could keep the morphology nearly unchanged even after 100 compression-rebound cycles,which indicates that GA has excellent compression resilience.?4?Due to its porosity and hydrophobicity,GA has a high adsorption capacity for organics.The adsorption experiments of liquid toluene and gaseous benzene series of the graphene aerogel before and after the addition of TEOS?GA and TEOS-3?showed that the addition of TEOS could modify the pore structure of the aerogel.TEOS decreased its average pore diameter,increased its specific surface area and improved its surface hydrophobicity of GA,thus greatly improving its adsorption capacity.The adsorption capacity of graphene aerogel for liquid toluene increased from 60 times?GA?to 72 times?TEOS-3?of its own weight,and its adsorption capacity for gaseous benzene increased from 201.7 mg/g?GA?to 809.51 mg/g?TEOS-3?.