Preparation And Electrochemical Performances Of Nitrogen-containing Graphene/carbon Nanohorns Composites

Graphene is considered as a preferred electrode material of supercapacitor because of its unique electronic structure,excellent physical and chemical properties.However,graphene reunites easily by van der Waals force between graphene layers,reducing the effective utilization of specific surface area and influencing the electrochemical property of graphene.In this thesis,in order to resolve the reunion of graphene,nitrogen-containing precursors were first prepared with graphene oxide(GO)as the mixture,by adding different nitrogen dopants and different biomass feedstocks,respectively.Then,nitrogen-doped graphene and nitrogen-doped graphene/carbon nanohorns materials were fabricated by means of high-temperature pyrolysis method.That are implemented to adjust the physical and chemical properties of graphene.Nitrogen-doped graphene(NGT)was fabricated by simple co-pyrolysis of nitrogen-containing precursors with urea as nitrogen source and tea saponin(TS)as a surfactant in the presence of GO.The results showed that GO is successfully reduced and the nitrogen atom is successfully introduced into the crystal lattice of graphene.The NGT electrode material up to 292.6 F·g-1 at a current density of 1 A·g-1.Then,nitrogen-doped graphene/carbon nanohorns composites(NGTC and NGLC)was prepared by pyrolysis of graphene oxide,with carbon nanohorns(CNHs)as spacers,urea as nitrogen source,and TS,lignosulfonate(LS)as surfactants,respectively.The results showed that NGTC and NGLC possessed very thin and fluffy structures when the feed contents of CNHs and TS or LS were 20 mg.NGTC exhibits a high specific capacitance of 360 F·g-1 at a current density of 1 A·g-1 and high stability(97.74%of capacitance retention ratio after 2000 cycles at 100 mV·s-1 and 94.11%of capacitance retention ratio after 1000 cycles at 1 A·g-1),NGLC exhibits a high specific capacitance of 373.7 F·g-1 at a current density of 1 A·g-1 and high stability(95.97%of capacitance retention ratio after 2000 cycles at 100 mV·s-1 and 95.15%of capacitance retention ratio after 1000 cycles at 1 A·g-1),indicating excellent performances of NGTC and NGLC.When congo red(CR)was introduced into the KOH electrolyte,the specific capacitances of NGTC and NGLC were enhanced greatly at the concentration of CR was 1.0 mmol·L-1.NGTC exhibits a high specific capacitance of 860.1 F·g-1 at a current density of 1 A·g-1 and the retention of specific capacitance was 96.30%after 2000 cycles at a scanning rate of 100 mV·s-1;NGLC exhibits a high specific capacitance of 623 F·g-1 at a current density of 1 A·g-1 and the retention of specific capacitance was 95.78%after 2000 cycles at a scanning rate of 100 mV s-1.