Selective Incorporation of Aqueous-Phase SWNTs into Pine Cones: A Unique Route to Creating Versatile Carbon Precursors for Electrode Materials

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 m(2) 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.