Synthesis, characterisation and carbon dioxide capture capacities of hierarchically porous Starbons®

Abstract

The synthesis of hierarchically porous Starbon^® based materials from initially highly mesoporous Starbons^® is reported. Mesoporous starbons^® are prepared from three different biopolymers: starch, alginic acid and pectin and each is then activated using three different activating agents: potassium hydroxide, carbon dioxide and oxygen to give a set of hierarchically porous Starbons^® which retain the mesopores of the precursor whilst becoming predominantly microporous. The hierarchically porous materials are characterised using nitrogen porosimetry, CHN analysis, ICP-OES, XPS, SEM and TEM imaging. It is shown that the hierarchically porous Starbons^® have higher carbon dioxide adsorption capacities than either the mesoporous Starbon^® precursors or conventional microporous activated carbon. The materials show selectivities of up to 64 for adsorption of carbon dioxide versus nitrogen and only lose only 3–7% of their carbon dioxide adsorption capacities when the carbon dioxide is saturated with water. The carbon dioxide capture capacity of all 50 Starbon^® materials showed a strong and positive linear correlation with the product of the materials ultramicropore surface area and ratio of ultramicropore (0.4–0.7 nm) volume to total pore volume.