| Porous chars, charcoal, and activated carbons have been exploited as catalysts, catalyst supports and adsorbents, but because of their complex chemistry, precise knowledge and control of carbon structure remains a challenge. Inspired by the promise of carbon nanotubes, the primary goal of this research has been the synthesis and characterization of nanoporous carbons prepared from pyrolysis of a suitable precursor on the pore surface of an inorganic template.; Previous models of amorphous, non-graphitizing pyrolytic carbons are chemically unrealistic, or they fail to reproduce the short range order seen in these materials. Here, a chemically realistic model for the structure of a non-graphitizing carbon is built by randomly incorporating non-hexagonal rings into an extended graphene sheet. We show that the pair distribution function (PDF) for models containing approximately 1% non-hexagonal rings has a remarkable similarity to the experimental PDF of carbon prepared from polyfurfuryl alcohol pyrolyzed at 1200°C.; We show for calcination at 500°C, the silica template SBA-15 exhibits a combination of mesopore and micropore structure, and the micropores are a manifestation of the fractal surface of the SBA-15 mesoporous channels. Calcination at higher temperature results in smaller unit cell, smaller mesopores and a smooth mesopore surface. NMR studies show a commensurate decrease in the concentration of Q3 silicon with decreased surface area; indicating the loss of Q3 by condensation to Q4 is the primary mechanism for the loss in microporosity. We synthesize and characterize ordered mesoporous ordered carbons from pyrolysis of sucrose or furfuryl alcohol in the pores of the SBA-15. We show that the carbon pore structure is strongly dependent on the choice of precursor, and much less so on SBA-15 pore geometry. We describe a hydrothermal etching effect the silica has on the carbons. We develop new information regarding the local structure of these materials from NEXAFS spectroscopy, and we show the pair-distribution function calculated from high-energy synchrotron scattering measurements. We conclude that these findings provide valuable insights for efforts aimed at templating carbon nanotubes inside porous inorganic substrates, and offer suggestions for future research. |
