The use of tannin to prepare carbon gels. Part I: Carbon aerogels

Tannin–formaldehyde carbon aerogels were prepared based on organic gels obtained by sol–gel polymerisation of tannin with formaldehyde that have been dried with supercritical acetone and pyrolysed at 900 °C. Tannins drastically reduce the cost of the gels, typically by a factor five, and polymerise in a wide range of pHs, leading to porous carbonaceous materials whose mesopore fraction ranges from 57% to 78%. The surface area and the total porosity can be as high as 715 m2 g−1 and 95%, respectively. Pore volumes and micro-mesopore-size distributions are similar to those of much more expensive carbon aerogels derived from resorcinol–formaldehyde resin. However, more easily adjustable pore textures may be obtained using tannins as precursors.