| Graphene has attracted a variety of research interests since it was first prepared by mechanical stripping method.Graphene have demonstrated promise in a wide variety of fields,including electronic devices,transparent electrodes,organic optoelectronic devices,super capacitors and multi-functional composite materials,due to its excellent electronic properties,mechanical properties,optical properties,stable chemical properties,temperature characteristics and unique two-dimensional nano-properties.Prepared with two-dimensional graphene,the graphene aerogels are three-dimensional porous and ultra-light material,which not only has the advantages of electronic properties,mechanical properties and chemical stability of two-dimensional graphene,but also has special properties such as high specific surface area.Graphene aerogels can be used in hydrogen storage,environmental management,supercapacitors and so on.In this paper,graphene oxide was prepared by the Hummers method.The graphene-based hydrogels were prepared by chemical reduction in constant temperature water bath,and then freeze-dried to obtain three-dimensional porous ultra-light graphene aerogels.The main aim of this paper is to increase the electrochemical properties of graphene aerogels and thus to improve the performance of supercapacitors.The main research contents are as follows:?1?The preparation process of the graphene hydrogel was investigated and the preparation conditions were optimized.The nitrogen-doped graphene hydrogels have been successfully preparation by chemical reduction self-assembly method by dispersing lysine,lysine,histidine,tryptophan,proline,and aminoacetic acid into the graphene oxide dispersion,respectively.The as-preprared graphene hydrogels were freeze-dried to obtain the graphene aerogels.SEM,XRD,IR spectra and XPS technologies were used to investigate the microstructure of the graphene aerogels.It was found that the doping amount of nitrogen in the aeorgels will be different with the different kinds of amino acids.The proportion of graphite type,pyrrole type,and pyridine type-nitrogen in different aerogels is not the same.The electrochemical test results demonstreted that the doping of nitrogen significantly improved the electrochemical performance of the graphene aerogels.The nitrogen doped aerogels prepared with proline was found to have the best electrochemical performance(specific capacitance up to 280.7 F·g-1)and electrochemical stability.?2?The nitrogen,sulfur co-doped graphene aerogel were prepared by using thiourea and thioacetamide as doping source.XPS results showed that N and S atoms had doped into graphene units.However,electrochemical test results showed that the co-doped aerogels have poor electrochemical properties.The detailed reasons still need further analysis.?3?The silver nanowires with high aspect ratio were prepared by polyol method.The silver nanowires/graphene composite aerogels were successfully prepared by using these silver nanowires.SEM,XRD,FT-IR,compressibility,conductivity and electrochemical properties of the silver nanowires/graphene composite aerogels were characterized and investigated.SEM images showed that silver nanowires were incorporated into the 3D structure of graphene aerogels,leading to the aerogels with excellent compressibility and recoverability,and improved electrical conductivity.Moreover,when the composite aerogels were compressed,the resistance changes obviously,and the resistance is directly proportional to the compressibility.In addition,the silver nanowires/graphene composite aerogels have excellent electrochemical properties with specific capacitance up to 228.7 F g-1,and have higher specific capacitance. |
PDF Full Text Request