Preparation of Macroporous Conductive Carbon Cerogels from Pyrolysis of Isocyanate-Crosslinked Resorcinol Formaldehyde Aerogels
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Carbon aerogels combine typical aerogal properties such as high surface area and low density with electrical conductivity. They are prepared by pyrolysis under N2 or Ar at 600-2100 degrees C of resorcinol formaldehyde (RF) aerogels, which in turn are prepared via aqueous sol-gel chemistry. Carbon aerogels are considered for numerous applications such as separation media in HPLC, as supercapacitors, as materials for hydrogen storage, as non-reflective materials, and as anodes in lithium-ion batteries. Meanwhile, porous carbons with high hydrophobic surface areas and large pore volumes are used as industrial adsorbents. In addition, macropores enhance mass transport for applicatoins in energy storage and lithium intercalation batteries. It is well-established with silica that monodispersed polystryrene beads can be used to introduce ordered mesoporosity or macroporosity. In the same approach, plystyrene beads have been also incorportated as templates in RF sol-gel matrices and have been removed later by dissolving in toluene. Here, we report that RF gels crosslinked with isocyanates yield macroporous, electrically conducting carbon aerogels without need for templating.