Low-density graphitic films prepared from iodine-doped enzymatically synthesized amylose films as carbonization precursors.

We have developed a novel approach for preparing low-density graphitic films using iodine-doped enzymatically synthesized amyloses (ESAs) with strictly controlled molecular weights as carbonization precursors. All of the iodine-doped ESA films retained their film structures and morphologies, even after the heat-treatment at 800 °C and 2600 °C. Therefore, iodine doping plays an indispensable role in retaining film structure and morphology during the carbonization of ESA polysaccharides. It was also elucidated that the carbonization yields of the ESA films can be controlled by changing the conditions of iodine doping process. The bulk densities of the graphitic films are varied from 0.08 to 0.42 g/cm3 dependent on the doping level. In addition, the capacitance performances of the graphite films prepared from the ESAs are investigated using cyclic voltammetry and galvanostatic charge/discharge procedures. The potential utility of the carbonized and graphitized ESA films for supercapacitors was revealed. This approach may broaden the application and even the swill processing of polysaccharides.

Conjugated polymer-based carbonaceous films as binder-free carbon electrodes in supercapacitors.

We present a facile preparation method for carbonaceous film electrodes using poly(3,4-ethylenedioxythiophene) (PEDOT) and polyacetylene (PA) films as precursors via a morphology-retaining carbonization process. Carbonization was performed on acceptor-doped conjugated polymer films in the temperature range of 600-1100 °C. The obtained carbonaceous films had similar surface morphologies to those of the original conjugated polymer films. The carbonaceous film prepared from the electrochemically synthesized PEDOT film and the carbon film prepared from the chemically synthesized PA film showed hierarchical porous structures consisting of granular and fibril morphologies, respectively. The PEDOT and PA films carbonized at 1100 °C exhibited average electrical conductivities of 2.1 × 100 S cm-1 and 9.9 × 101 S cm-1, respectively. The carbonaceous films could be used as binder-free carbon electrodes in supercapacitors, and the PEDOT-based carbonaceous film prepared in the range of 1000-1100 °C exhibited the most efficient performance on the basis of the electrochemical capacitance in neutral and alkaline aqueous solutions determined from cyclic voltammograms and galvanostatic charge/discharge curves. This approach requires no binders/additives and no further activation processes or additional treatments for the enhancement of the capacities of the carbon materials, enabling one-step fabrication and their direct use as carbon electrodes for energy-storage devices. This is the first report of PEDOT- and PA-based carbonaceous films being used as carbon electrodes in supercapacitors.

Helical carbon and graphite films prepared from helical poly(3,4-ethylenedioxythiophene) films synthesized by electrochemical polymerization in chiral nematic liquid crystals.

Helical carbon and graphite films from helical poly(3,4-ethylenedioxythiophene) (H-PEDOT) films synthesized through electrochemical polymerization in a chiral nematic liquid-crystal (N*-LC) field are prepared. The microscope investigations showed that the H-PEDOT film synthesized in the N*-LC has large domains of one-handed spiral morphology consisting of fibril bundles. The H-PEDOT films exhibited distinct Cotton effects in circular dichroism spectra. The highly twisted N*-LC with a helical pitch of smaller than 1 µm produced the H-PEDOT film with a highly ordered morphology. The spiral morphologies with left- and right-handed screws were observed for the carbon films prepared from the H-PEDOT films at 800 °C and were well correlated with the textures and helical pitches of the N*-LCs. The spiral morphologies of the precursors were also retained even in the graphite films prepared from the helical carbon films at 2600 °C.