Effect of the Position of Amine Groups on the CO<sub>2</sub>, CH<sub>4</sub>, and H<sub>2</sub> Adsorption Performance of Graphene Nanoflakes
Sangmin Park, Junghoon Yang, Hye‐Min Lee, Young‐Seak Lee, Youn‐Kyoung Lee, Yasuhiro Yamada, Nodo Lee, Jungpil Kim
Abstract
CO 2 separation from CO 2 /CH 4 and CO 2 /H 2 mixtures is essential in H 2 production from biogas. Although amine-functionalized carbon materials are excellent candidates for selective CO 2 adsorption, their adsorption performance depends on the amine edge position, which requires further clarification. Herein, 19 graphene nanoflakes (GNFs) bearing two amines at various positions on the zigzag, corner, and armchair edges were evaluated. All structures exhibited better CO 2 adsorption compared to CH 4 and H 2 . In the GNFs with isolated amines, only one main bond (H 2 N – C O 2 ) was involved in CO 2 adsorption, which was influenced by charge transfer from the GNFs to CO 2 . GNFs with adjacent amines had an additional hydrogen bond ( H 2 N–C O 2 ) that became stronger with decreasing steric hindrance. The CO 2 adsorption performance of amines decreased as the number of methyl groups on the nitrogen increased, which interfered with CO 2 adsorption. The presence of H 2 O hindered the interaction of amines and CO 2 owing to the strong hydrogen bond between H 2 O and amines.