It is important to fabricate nanostructured architectures comprised of functional components for a wide variety of applications because precise structural control in the nanometer regime can yield unprecedented, fascinating properties. Owing to their well-defined microstructural characteristics, it has been popular to use carbon nanospecies, such as nanotubes and graphene, in fabricating nanocomposites and nanohybrids. Nevertheless, it still remains hard to control and manipulate nanospecies for specific applications, thus preventing their commercialization. Herein, first, we report unique one-dimensional nanoarchitectures with meso-/macropores, consisting of single-walled nanotubes (SWNTs), graphene, and polyacrylonitrile, in which poly(vinyl alcohol) was employed as a dispersing agent and sacrificial porogen. One-dimensional SWNTs and two-dimensional graphene pieces were combined in the confined interior space of electrospun nanofibers, which led to unique microstructural characteristics such as enhanced ordering of SWNTs, graphene pieces, and polymer chains in the nanofiber interior. Next, the SWNT/graphene-in-polymer nanofiber (SGPNF) structures were converted into carbonized products (SGCNFs) with effective porosity and tunable electrochemical properties. Similar to SGPNFs, the microstructural and electrical properties of the SGCNFs depended on the incorporated amount of SWNT and graphene. At higher SWNT content, the mesopore volume proportion and specific discharge capacitance of the SGCNFs increased by max. 63 and 598%, respectively. The SGCNFs showed strong potential as a high-performance electrode material for electrochemical capacitors (max. capacitance: nonactivated ∼390 F g −1 and activated ∼750 F g −1 ). Flexible, all solid-state capacitor cells based on SGCNFs were also successfully demonstrated as a model application. The SGCNFs can be further functionalized by various methods, which will impart attractive properties for extended applications.
Nature presents delicate and complex materials systems beyond those fathomable by humans. This work demonstrates the use of pine cones as a biomass mold for creating new metal/carbon nanohybrids.
Selective impregnation
of single-walled carbon nanotubes (SWNTs)
into the interior of pine cones was achieved via inherent folding
actuation of the cone by water absorption. Individually dispersed
aqueous-phase SWNTs were incorporated into the cone along the pathway
of water absorption, and consequently, a concentrated SWNT inclusion
was formed on the scales of the cone. To fully exploit its properties
as a carbon precursor, the cone was further treated with potassium
hydroxide (KOH) solution. The KOH treatment altered the qualitative
properties of the cone, which was used to generate activated carbons,
and led to swelling of the cell wall of the cone to ultimately increase
the size of the pores formed via carbonization. Inclusion of the SWNTs
in the cone and the effect of KOH treatment were determined by the
characteristics of the constituent tissues of the cone, which offered
the opportunity of achieving tissue-dependent textural and electrochemical
properties of the carbonized cones. Representatively, the activated
and SWNT-impregnated carbonized cone sample (from a specific part
of the scale) possessed the optimized properties of high surface area
(639 m2 g–1) and high specific capacitance
(310 F g–1). As a model application, the carbonized
cone was evaluated as an electrode material for electrochemical capacitors,
and demonstrated energy and power densities exceeding those of previously
reported biomass-derived carbons. Our approach provides more options
for improving the properties of biomass-derived carbons. Furthermore,
it is expected to provide a useful way to bridge the dimensional gap
between the nanocarbon species and the biomass precursors to promote
commercialization of the materials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.