Graphene Nanoribbons And Their Composites: Preparation And Property

Graphene nanoribbons can be regarded as unfolded carbon nanotubes or ribbon-likegraphene.They act as the bridge between one-dimensional carbon nanotubes and two-dimensional graphene.Graphene nanoribbons have similar structures and properties to graphene and carbon nanotubes.As a new type of nano-carbon material,graphene nanoribbons possess large aspect ratio,good conductivity,rich active edge sites and excellent mechanical properties,and promising applications in the fields of catalysis,energy storage and sensors.In the present thesis,we focus on the preparation and assembly of graphene nanoribbons.Three-dimensional graphene nanoribbon aerogels are created with the assistance of Pickering emulsions,and composite materials of graphene nanoribbons and metal organic frameworks(MOF)-derived carbons are prepared with the combination of in situ growth and thermal treatment.The main research contents are presented as follows:(1)Graphene nanoribbons are prepared via longitudinal unzipping carbon nanotubes.The graphene nanoribbon aerogels are fabricated using Pickering emulsions as soft template and poly(propylene glycol)bis(2-aminopropyl ether)as co-surfactant and cross-linker.It is revealed that the aerogels prepared at the water/oil ratio of 7:1 possess the uniform pore structure and excellent mechanical properties.The aerogels exhibit remarkable shape recovery after 1000 cycling compressions with 50% deformations.Furthermore,the structure can fully recover from 95% compression after 50 cycles.The as-prepared aerogels exhibit outstanding electromechanical performance.Our graphene nanoribbon aerogels may find potential applications in the fields of energy absorption,electrochemical energy storage,as well as environmental protection.(2)The composites of ZIF-8 and graphene oxide nanoribbons are prepared by in-situ growth at room temperature,and MOF-derived carbon/graphene nanoribbon composites(GNR@NPC)are prepared through thermal annealing procedure followed by acid treatment.The nitrogen content in the composites is 15.32% by weight.When used as cathode material in lithium-sulfur batteries,GNR@NPC exhibit a high specific capacity of 458.2 m Ah g-1at a high current density of 4 C.After 300 cycles at a current density of 1 C,the specific capacity can still reach 504.9 m Ah g-1 with an ultralow capacity decay of 0.1% per cycle.This outstanding electrochemical performance are attributed to the synergistic effect of well-developed pore structure and high nitrogen-induced sulfur adsorption,which caneffectively increase the conductivity and suppress the sulfur shuttle effect and volume expansion.As a result,the materials show excellent cycle performance and rate performance.