Abstract
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.
Highlights
The scientific significance and public perception of anthropogenic climate change are increasing significantly,[1] as the fraction of CO2 in the atmosphere has reached 407 ppm and is still growing
Structure and chemistry By electrospinning and carbonization at different temperatures ranging from 600 to 1100 8C, Carbon nanofibers (CNFs) mats were prepared from a 10 wt % PAN solution
None of the nonpost-treated carbons reaches the extraordinarily high adsorption selectivity of the currently investigated carbons. The latter are only matched by tailor-made metal–organic frameworks (MOFs) and very few posttreated carbons,[21,66] which potentially enables the practical application of the electrospun CNFs in gas separation processes with feed gases having relatively small CO2 fraction
Summary
The scientific significance and public perception of anthropogenic climate change are increasing significantly,[1] as the fraction of CO2 in the atmosphere has reached 407 ppm and is still growing. Afterwards, the PAN polymer chains are stabilized and cross-linked in air and carbonized in argon to yield carbon fibers in the submicrometer range, that is, CNFs, which have a very high surface area.[41] The elemental composition and the pore properties of the as-prepared CNFs are finely adjustable by means of the carbonization temperature, and excellent low-pressure adsorption capacity and selectivity towards CO2 are attainable. By tailoring the ultramicropore system (micropores < 0.7 nm)[42] it is possible to achieve ideal adsorbed solution theory (IAST) selectivities of 350 at a low pressure of 20 mbar and 132 at 1 bar Both values are very close to typical results for MOFs, among the highest values for carbon materials reported so far, and the highest values for unmodified carbons
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