Three-dimensional Composite Of Carbon Nanotubes/Graphene For The Stability Mechanism Of Nano-fusion

Currently,carbon nanomaterials are a type of hot materials in material science,such as carbon nanotubes(CNTs),graphene,fullerene(C60),graphene quantum dot(GQD)and so on.These carbon nanomaterials show high specific surface area,good conductivity,and excellent mechanical properties,resulting in these carbon nanomaterials outstanding in many fields.Despite these advantages,the structural limitations of low-dimensional nanomaterials limit their applications.For example,CNTs can only transport ions/electrons along the axial direction,and Graphene can only transport the substances in the plane when as a carrier.Therefore,researchers usually combine two or more type carbon nanomaterials,and even construct a threedimensional structure to solve this problem,improving the performance of carbon materials,and further expanding the application of the carbon materials.In this paper,one-dimensional CNTs and two-dimensional Graphene were chosen as research objects.Combining the advantages of the two different dimensions of carbon nanomaterials,a carbon hybrid with three-dimensional network structure was designed and prepared.Furthermore,the as-prepared carbon hybrid was employed as conductive substrate for sulfur and enzyme.The electrochemical properties of sulfur cathode composites and enzyme electrodes were studyed and the stability mechanism and electron transport mechanism were futher explored.In addition,the threedimensional network structure is used as a skeleton,which is further combined with zero-dimensional carbon nanomaterials(such as C60 and GQD).The designed conductive network was employed as host for sulfur and the electrochemical properties of the composites were investigated as electrodes of Li-S batteries.The main contents are as follows:(1)Three-dimensional graphene/carbon nanotube(CNTs/G)composite material was prepared by a one-step hydrothermal method.Interestingly,nanofusion area was formed on the surface between carbon nanotubes and Graphene,not only improving the structural stability of three-dimensional network,but also facilitating the eletron transfor between the two-phase interface.Furthermore,the 3D network structure maintained well after the treatments in boiling water and steam for 168 hours.When as a conductive host for sulfur and biological enzyme,the three-dimensional conductive network promotes the rapid transfer of electrons of chemical reaction,thus exhibiting excellent electrochemical performances.(2)The zero-dimensional carbon nanomaterial—GQD were introduced into the three-dimensional framework of CNTs/G by one-step hydrothermal method.The aminated GQD can firmly anchor on the surface of three-dimensional skeleton,endowing more electrochemical active sites to the composite.Therefore,the electrochemical cycling stability is superior to the three-phase composite.(3)In the one-step hydrothermal process,another zero-dimensional carbon nanomaterial,fullerene C60,was introduced to prepare carbon nanotube/graphene/C60(CNTs/G/C60)three-phase composite carbon nanomaterial.When used as conductive host for sulfur,the surfur cathode exhibited better electrochemical cycling stability than the surfur cathode in Chapter 2 whose condutive network was only a two-phase carbon nanomaterial,illustrating that the addition of zero-dimensional carbon materials could further improve the electron/ion transport of the two-phase conductive networks.