Effect of pore size on carbon dioxide sorption by carbide derived carbon

Abstract

CO₂ sorption at atmospheric and sub-atmospheric pressures is a key step towards carbon capture and sequestration (CCS) and materials capable of fast and efficient CO₂ uptake are currently being studied extensively. Carbide-derived carbons (CDCs) show a very high sorption capacity for CO₂ of up to 7.1 mol/kg at 0 °C and ambient pressure. This value is significantly higher than other carbon materials. Systematic experimental investigation of a large number of different CDCs derived from nano- and micrometer sized precursors with and without activation show a linear correlation between the CO₂ uptake at a certain pressure and the pore volume. However, CO₂ sorption is not limited by the total pore volume but only by pores smaller than a certain diameter. At 1 bar, pores smaller than 0.8 nm contribute the most to the CO₂ uptake and at 0.1 bar pores smaller or equal to 0.5 nm are preferred. With lower total pressure, smaller pores contribute more to the measured amount of adsorbed CO₂. The prediction of the CO₂ uptake based on the pore volume for pores of a certain diameter is much more accurate than predictions based on the mean pore size or the specific surface area. This study provides guidelines for the design of materials with an improved ability to remove carbon dioxide from the environment at atmospheric and lower pressures.