The Preparation Of Modified Graphene Oxide And The Study Of Its Supercapacitor Performance

Graphene oxide has been an ideal supercapacitor electrode material owing to its high electrical conductivity,high specific surface area,and rich surface functional groups,easy to surface-modified and self-assembled to form a hierarchical structure.This thesis studies the self-assembly surface modification and nitrogen doping modification of graphene oxide to suppress the graphitization accumulation of reduced graphene oxide and improve its supercapacitor performanceUsing concentrated sulfuric acid as the solvent,nanocomposites of iron（Ⅱ）phthalocyanine and graphene oxide（dennoted as FePcGOn）are rationally and facilely fabricated by self-assembly viaπ-πinteractions.The unique structure of FePcGO2render the nanocomposites greatly improved conductivity and accelerated rates of both charge transfer and electrolyte migration.The tightlyπ-πstacking between FePcand GO bestows the materials structural stability.The molecularly dispersive FePccontributes much pseudocapacitance to elevate the energy density of supercapacitor.Three-electrode test reveal a high specific capacitance of 514 F g^-1 for FePcGO2 at a current density of 1 Ag^-1 over potential window of 1 V.A capacity of 90 F g^-1 sustains at an ultrahigh current density of 500 Ag^-1.Symmetrical two-electrode supercapcitor also demonstrate excellent supercapacitive properties of FePcGO2 and delivers a capacitance of 235.6 F g^-1 at 1 Ag^-1 over 1 V.The device keeps capacity of 31 F g^-1at 500 Ag^-1.A steady capacity of 200.2 F g^-1 sustains at 5 Ag^-1 after 60000 cycles.An energy density of 8.26 Wh kg^-1 achives at 1 Ag^-1 over 1 V.FePcGO2 also exhibits stability and further improved performances over high voltage windows.Symmetrical FePcGO2 supercapacitor achieves high capacity of 308.6 F g^-1 and energy density of21 Wh kg^-1 over 1.4 V at 1 Ag^-1.The present work provides insights into high performance supercapacitive materials.The nitrogen-doped reduced graphene oxide DMFr GO was simply prepared by solvothermal method using N,N-dimethylformamide（DMF）as the dispersant and reductant.Dimethylamine is obtained by hydrolysis of DMF at high solvothermal temperature.Owing to the functional nature,dimethylamine can react with carboxylic groups of layers of GO,forming covalently structures between GO and dimethylamine Aggragation of N-doped r GO generated microporous structure.The doped nitrogen species exist in pyridinic nitrogen,pyrrolic nitrogen,and graphitic nitrogen.Three-electrode test reveal a high specific capacitance of 287 F g^-1 for DMFr GO180 at a current density of 1 Ag^-1 over potential window of 1 V.A capacity of 192 F g^-1 at high current density of 100 Ag^-1,indicating excellent rate performance.A high loading electrode of 5 mg cm^-2still provides a high capacitance of 230 F g^-1 at a current density of 1 Ag^-1 and 129.5 F g^-1 at current density of 100 Ag^-1.The electrode exhibit high capacitance。Initial capacity of 232 F g^-1 during charge and discharge at a large current of 20 Ag^-1.After 1000 cycles,the capacity retention rate of 94.8% indicates excellent cycle stability.