Carbon nanofibers (CNFs) derived from electrospun polyacrylonitrile (PAN) were investigated with respect to their gas adsorption properties. By employing CO2 adsorption measurements, it is shown that the adsorption capacity and selectivity of the fibers can be tailored by means of the applied carbonization temperature. General pore properties of the CNFs were identified by Ar adsorption measurements, whereas CO2 adsorption measurements provided information about the ultramicroporosity, adsorption energies, and adsorption capacities. Ideal adsorbed solution theory (IAST) selectivities under practically relevant conditions were determined by evaluation of single-component data for N2 and CO2 . Especially for low carbonization temperatures, the CNFs exhibit very good low-pressure adsorption performance and excellent CO2 /N2 IAST selectivities of 350 at 20 mbar and 132 at 1 bar, which are attributed to a molecular-sieve effect in very narrow slit pores. These IAST selectivities are some of the highest values for carbon materials reported in the literature so far and the highest IAST selectivities for as-prepared, non-post-treated carbon ever.
Keywords: adsorption; carbon; carbon dioxide capture; molecular sieves; nanofibers.
© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.