Modified graphene and carbon nanotube based nanostructures and their applications

Abstract

Outstanding pristine properties of graphene and carbon nanotubes(CNTs) have gathered many research interests. However, the scope for applications were limited without precise control of the material structures and properties. Therefore tremendous efforts were devoted to the chemical modification/doping of CNTs and graphene and their relevant applications with optimized structures and properties. The practical benefits from chemical modification/doping includes the controllability of electronic energy level, charge carrier density, surface energy and surface reactivity for diverse advanced applications, namely flexible electronics/optoelectronics, energy conversion/storage, nanocomposites, and environmental remediation. Here, I present tailored modified graphene and CNTs based nanostructures and expand the scope to their applications. Firstly, graphene was oxidized as graphene oxide to get higher surface energy for stable aqueous dispersion. Graphene oxide aqueous dispersion showed nematic liquid crystallinity, which is a new class of carbon based functional nanostructure. Graphene oxide liquid crystal was further modified by compositing with nanoparticles and polymers for applications such as fibers. Secondly, CNTs were N-doped to lower the work function of the CNTs. N-CNTs were composited with amorphous cobalt hydroxide which is oxygen evolution catalyst. It is demonstrated that N-dopants at CNT surface successfully enhanced 4e reduction pathway during ORR by lowering work function of the CNT. Furthermore the unique sub-nanometer scale coated morphology along with strong cobalt species-NCNT interaction minimized the deactivation of catalyst during cycles. The amorphous cobalt hydroxide NCNT hybrid was tested as primary and secondary $Zn-O_2$ battery, showing stable catalytic activity. New functional nanostructures composed of chemically modified graphene and hetero atom doped CNTs can broaden up applications of graphene and CNTs for nanocomposites and energy conversion/storage system.