The Preparation Of Graphene Electrode Materials And The Application In Supercapacitors

Graphene,a new two-dimension carbon material,possesses many outstanding properties derived from the honeycomb structure formed by monolayer sp2-hybridized carbon atom,such as high electronic mobility and large specific surface area.These properties make graphene become an ideal electrode materials and be used in energy storage.Moreover,graphene with excellent conductivity can be used to improve other inferior electrode materials.When graphene act as supporter,the special two-dimension plan structure and its large specific surface area for coating granular electrode materials to improve the electrode materials structure stability.But,the monolayer structure of graphene is not stable.The graphene layers trend to agglomerate into graphite forced by π-π between two gaphene layers under thermal dynamics drive force,which dramatically decrease its specific surface area and sharply reduce electrical conductivity,and further limit the full reflection of function properties when graphene served as electrode materials.Therefore,these stack and restack that damage electrochemical performance become a difficulties andchallenges in preparing the high-performance graphene supercapacitor field.For another,improving electrode materials density to reduce energy storage device volume also have been the development direction.In this research work,in order to avoid the graphene layers agglomeration,two different structure design and construction,graphene/porous carbon and porous graphene films,were used to electrode materials in supercapacitor and investigate its properties.The main research works are as follows:1.The regularly porous metal-organic framework,MOF-5,was synthesized by precipitation and solvothermal method.And the porous carbon materials(MOFC)were obtained by further high-temperature carbonization.A series of MOFC was producted after MOF-5 was processed by different time of solution ageing and solvothermal reaction.The preferable carbon materials,MOFC-d3-26,was selected by electrochemical performance,to prepare for graphene/porous MOF carbon materials.2.The graphene/porous MOF carbon materials composite films(GM)were prepared by intercalation and chemical reduction.The GM combine the large specific surface area and porosity of graphene and MOFC,and possesses high electrochemical performance when used by electrode material.This intercalation methode also solve the graphene agglomeration.3.The porous graphene films(PGF)were prepared by in-situ synthesis.Fist,the graphene oxide was modified by zinc acetate(Zn(CH3COO)2),the Zn2+ adhered to the graphene oxide layers.ZnO/Zn(OH)2 modified graphene materials(PGZF)were formed under hydrothermal reaction and reduction of hydrazine hydrate and alkali.The three-dimension porous and densely packed graphene film was formed after removing ZnO/Zn(OH)2.In addition,ZnO/Zn(OH)2 intercalated between graphene can efficiently prevent graphene layers restack during filtrating into films.The porous structure of PGF can be retained after removing ZnO/Zn(OH)2 of PGZF.The free-standing PGF possesses excellent gravimetric capacitance and volumetric capacitance,simultaneously.