Synthesis and characterisation of control porosity resorcinol formaldehyde based carbon aerogels under different conditions

Highly porous carbon aerogels are synthesised by sol-gel polymerisation of resorcinol (R) and formaldehyde (F) using sodium carbonate (C) as catalyst followed by carbonization under steady flow of argon (Ar). The effect of resorcinol / catalyst (R/C) ratio and carbonization temperature on the porous structure of resultant gels and carbons was investigated using nitrogen adsorption-desorption measurements at -196 ºC. By controlling the R/C ratio between 100-500 and carbonization temperature between 800-100 ºC, carbon aerogels with specific surface area (SSA) ranging between 537-687 m2 g^-1 and average pore size in the of 1.80 - 4.62 nm can be produced. it has been shown that carbonization had significant effect on the porous structure of the resultant carbon aerogels, decreasing the pore size and increasing the microporosity of the carbon due to the shrinkage of the nanostructure and the formation of microporosity within the gel structure. Substantial change in micro structure of carbon aerogels was observed at carbonization temperature of 800 ºC which resulted in highest specific surface area and pore volume without any considerable change in average pore size. BET specific surface area and pore volume increased from 687 to 1775 m² g^-1 and 0.24 to 0.94 cm³ g^-1 respectively whereas the pore size remained constant (around 2nm) after physical activation of the carbon aerogels using CO₂ as an activation agent.