(562d) Atomically Thin N-Based Graphene Membrane with Enhanced Adsorption and Size-Sieving Effect

Single-layer graphene membrane has been regarded as an ideal candidate for gas separation due to the fact that atomic thickness has low mass transport resistance for high throughput permeance while holding an attractive molecular selectivity¹. However, achieving its promise still remains a bottleneck for high-performance gas separation. It is attributed to the incorporation of sub-angstrom resolution nanopores on the graphene lattice is a challenge to control for separating the similar size gas pair^2,3, such as CO₂/N₂ and O₂/N₂. To address this, functionalizing the graphene nanopores leads to preferential adsorption and potentially narrows down the gap between electron clouds along the pore edge, which is expected to achieve high-performance separation.

In this presentation, I will introduce new N-based graphene hosting atomic-scale functional groups on the pore edges (Figure 1). Briefly, NH₃ was introduced into the O₃-treated graphene lattice via reacting with the O-functional groups on the graphene lattice⁴. This leads to the formation of amine groups and doped N on the graphene surface. CO₂ chemisorption was observed via zwitterion reaction by near ambient pressure X-ray photoelectron spectroscopy, providing insights into CO₂ adsorption coverage on the graphene nanopores. High-resolution transmission electron microscopy (HRTEM) images showed that N functional groups partially covered the pore size, proving that functional groups narrowed down the effective pore size for molecules to translocate.

Next, I will discuss the gas separation performance of N-based graphene by enhancing CO₂ adsorption and size-sieving. The molecular cut-off narrowed down to less than 0.2 Å, leading to O₂/N₂ selectivity of 6.0 with 1630 GPU of O₂ permeance. Apart from that, the atomic-scale amine groups and doped N on the pore edge preferentially adsorb CO₂ on the graphene lattice, leading to apparent activation energy down to 0.9 kJ mole^-1. This yields CO₂ permeance of 8900 GPU and a CO₂/N₂ separation factor of 140 for N-based graphene membranes.

References

(1) Wang, L.; Boutilier, M. S. H.; Kidambi, P. R.; Jang, D.; Hadjiconstantinou, N. G.; Karnik, R. Nat. Nanotechnol. 2017, 12 (6), 509–522.

(2) Huang, S.; Li, S.; Villalobos, L. F.; Dakhchoune, M.; Micari, M.; Babu, D. J.; Vahdat, M. T.; Mensi, M.; Oveisi, E.; Agrawal, K. V. Sci. Adv. 2021, 7, eabf0116.

(3) Hsu, K.-J.; Villalobos, L. F.; Huang, S.; Chi, H.-Y.; Dakhchoune, M.; Lee, W.-C.; He, G.; Mensi, M.; Agrawal, K. V. ACS Nano 2021, 15 (8), 13230–13239.

(4) Wang, X.; Li, X.; Zhang, L.; Yoon, Y.; Weber, P. K.; Wang, H.; Guo, J.; Dai, H. Science. 2009, 324 (5928), 768–771.