Carbonization and activation of sol-gel derived carbon xerogels

The effects of the carbonization temperature (in N-2) and CO2-activation time (in 5% CO2 in N-2) on the pore structure of carbon xerogels, derived from the sol-gel polymerization of resorcinol-formaldehyde resins, were studied in detail. As the carbonization temperature increased, the number of micropores in the 0.6 nm range decreased, with essentially no effect on the pores in the mesopore range, and the cumulative surface areas and pore volumes both decreased, but only marginally. As the CO2-activation time increased, the number of micropores and mesopores both increased, where pores in the 0.6 nm range eventually became pores in the 0.13 nm range, and the cumulative surface areas and pore volumes both increased significantly. The skeletal densities also increased significantly, approaching that of graphite, with an increase in both the carbonization temperature and CO2-activation time, but the nanoparticle size was largely unaffected. Weight loss was nearly independent of the carbonization temperature at about 50%, but it was strongly dependent on the CO2-activation time with a maximum weight loss of about 75%. (C) 2000 Elsevier Science Ltd. All rights reserved.