Dual‐Cation Activation of N‐Enriched Porous Carbons Improves Control of CO<sub>2</sub> and N<sub>2</sub> Adsorption Thermodynamics for Selective CO<sub>2</sub> Capture
J. Ehren Eichler, H. Wayne Leonard, Ethan Kang Yang, Lettie A. Smith, Samantha N. Lauro, James N. Burrow, Rui P. P. L. Ribeiro, C. Buddie Mullins
Abstract
Abstract Porous carbons have potential to facilitate energy‐efficient separation of CO 2 from post‐combustion flue gas. However, the complicated interplay between chemical and textural properties has prevented a comprehensive understanding of selective CO 2 adsorption. This study demonstrates how dual cation activation of carbons serves as a synthetic platform to help modulate porosity independent of nitrogen content. For samples derived from nitrogen‐poor precursors, surface areas deviated significantly (2200–4500 m 2 g −1 ) at a constant total nitrogen content (2.3 ± 0.3 at %). Surface area changed less for samples derived from nitrogen‐rich precursors (400–675 m 2 g −1 at 23.1 ± 0.1 at % N). Rigorous structure‐function and thermodynamic analysis of these carbons not only helped to uncover the nature of the different adsorption sites, but also established a fundamental linear free energy exchange relationship. This coupled with material property correlations informed the properties that facilitated selective capture of CO 2 . Critically, for these physisorptive carbons, selectivity is almost entirely a function of relative porosity and chemical adsorbent‐adsorbate interactions play a negligible role.