Inverse opal carbons derived from a polymer precursor as electrode materials for electric double-layer capacitors

Self-standing and macroporous carbon materials were prepared by using silica opals (colloidal crystal) as a template. Poly(furfuryl alcohol) was synthesized in the interstice of the silica colloidal crystals, followed by carbonization at 1000 degrees C. The silica templates were etched off to give inverse opal carbons. The inverse opal carbons were characterized by scanning electron micrograph (SEM), reflection spectroscopy, elemental analysis, infrared spectroscopy, X-ray diffraction, direct current conductivity, and N-2-adsorption/desorption experiments. The SEM images and the reflection spectra indicated periodic porous structures that were negative structures of the silica opal templates. The inverse opal carbons were hard carbons, mainly consisting of amorphous incompletely graphitized structures, and have electronic conductivity of 10(2) S cm(-1). The nitrogen adosorption/desorption experiments clarified that the carbons have large N-2-BET (Brunauer-Emmett-Teller) specific surface area resulting from a lot of mesopores, in addition to macropores based on the silica templates. Electric double-layer charging and discharging of the carbons were studied in a tetraethylammonium tetrafluoroborate/propylene carbonate solution. The electric double-layer gravimetric capacitance and the coulombic efficiency of the inverse opal carbon electrodes in the solution increased with a decrease in the diameter of the silica spheres used for the opal templates and became superior to those of a typical activated carbon. (c) 2008 The Electrochemical Society.