Preparation Of Graphene Nanoribbons And Their Application For Supercapacitor

As a new type of energy storage device,supercapacitor has the advantages of high power density,long cycle life and high reliability.And it is widely used in portable electronic equipment,electric vehicles and other fields.However,the manufacture of supercapacitor with high energy density is still a great challenge.Graphene nanoribbons possess large aspect ratio,rich edge positions,and excellent electrical conductivity.They show a broad application prospect in the field of high-performance supercapacitor electrode materials.Based on the novel structures of graphene nanoribbons,this dissertation focuses on the preparation oxygen-functionalized graphene nanoribbons and their composites?Co₃O₄/GNRs?for supercapacitor.The introduction of pseudocapacitance remarkably improves the overall electrochemical performance of the materials.The main research contents are as follows:Introducing oxygenated functionalities into carbon networks can provide additional pseudocapacitance for supercapacitor.However,excessive oxygen functional groups usually cause low electrical conductivity.Herein,we propose a strategy for tunable functionalization of edge-enriched graphene nanoribbons by means of dielectric barrier discharge?DBD?plasma.The functionalized graphene nanoribbons exhibit high specific capacitance owing to the suitable oxygen functional groups and the intrinsic edge-enriched structure.The assembled symmetric supercapacitor device based on as-prepared graphene nanoribbons exhibits a superior energy density of 12.65 Wh kg^-1,and 93.76%capacitance retention after10,000 cycles in 1 M Na₂SO₄ aqueous electrolyte.This work may find a new way to finely control functionalities on carbon nanomaterials for high-performance energy storage devices.The Co₃O₄/graphene nanoribbons composites?Co₃O₄/GNRs?are prepared through a simple co-precipitation and high temperature calcination process,and the Co₃O₄ loading is optimized by adjusting the mass ratio of the precursor cobalt nitrate to the graphene oxide nanoribbons.As a supercapacitor electrode material,the specific capacitance of Co₃O₄/GNRs-5 electrode material is 175 F g^-1 at 1 A g^-1,much better than that of the single Co₃O₄ or graphene nanoribbons.This composite electrode material can make the most of the pseudocapacitance of Co₃O₄ nanoparticles and the conductivity of graphene nanoribbons.There is a significant synergistic effect between the two materials.