Determination of the optimal pore size for improved CO ₂ adsorption in activated carbon fibers

Commercially available activated carbon fibers (ACFs) were modified further by a chemical activation method to obtain superior CO ₂ adsorption capacity. The relationship between the pore structure of the modified ACF and the CO ₂ adsorption behaviors was investigated. Chemical activation (with KOH at a fixed activation temperature of 900°C for 1h and various KOH/ACF weight ratios ranging from 1 to 4) of ACF increased the total pore volume and specific surface area to 1.124cm ³g ^-1 (KOH/ACF weight ratio of 2) and 2318m ²g ^-1 (KOH/ACF weight ratio of 4), respectively. Compared to ACF, the total pore volume and specific surface area were improved by factors of 2.5 and 2.3, respectively. Interestingly, the highest CO ₂ adsorption capacity of 250mgg ^-1 at 298K and 1bar was observed at a KOH/ACF weight ratio of 3. The modified ACF had the narrowest microporosity ranging from 0.5 to 0.7nm. Therefore, the increase in CO ₂ adsorption capacity after chemical activation is closely related to the narrower pore size distribution rather than the total or micropore volume and specific surface area.