Engineering Gas-Sieving Nanopores in Graphene with Sub-Å Resolution

Single-layer graphene-based membranes have been regarded as the ultimate gas separation membranes, capable of yielding ultrahigh gas permeance and an attractive molecular selectivity, attributing to their atomic thicknesses.¹ However, despite their promise, the attractive performance of atom-thick graphene membranes in the size-selective separation of gas mixtures has not been realized. The development of these membranes face two major bottlenecks: 1) crack-free fabrication of large-area membranes; 2) develop a controllable lattice etching technique mitigating the trade-off between the pore density and the pore-size distribution (PSD).

Herein, we reported several novel approaches to achieve record-high gas separation performance from single-layer graphene-based membrane. A novel nanoporous-carbon-assisted graphene transfer technique was developed, enabling the transfer of relatively large area single-layer graphene onto a macroporous support without inducing cracks or tears.² For the first time, gas-sieving from the intrinsic defects in the chemical vapor deposition derived graphene was observed. Attractive gas separation performances were achieved with the ultralow porosity of 0.025%. Furthermore, a synergistic strategy of decoupling pore-nucleation and pore-expansion on graphene lattice resulted in high-performance single-layer graphene membranes (H₂ permeance of 1340 to 6045 gas permeation units (GPU); H₂/CH₄ separation factor of 15.6 to 25.1).³ Moreover, millisecond graphene gasification was developed to realize high pore-density and narrow PSD nanoporous single-layer graphene, yielding record gas separation performance CO₂/N₂ selectivity of 24.4 with corresponding CO₂ permeance over 9550 gas permeation units.⁴ Overall, we demonstrate that graphene-based membranes are indeed capable of reaching the predicted high performance in gas separation.

References

(1) Wang, L.; Boutilier, M. S. H.; Kidambi, P. R.; Jang, D.; Hadjiconstantinou, N. G.; Karnik, R. Fundamental Transport Mechanisms, Fabrication and Potential Applications of Nanoporous Atomically Thin Membranes. Nature Nanotechnology 2017, 12, 509–522.

(2) Huang, S.; Dakhchoune, M.; Luo, W.; Oveisi, E.; He, G.; Rezaei, M.; Zhao, J.; Alexander, D. T. L.; Züttel, A.; Strano, M. S.; Agrawal, K. V. Single-Layer Graphene Membranes by Crack-Free Transfer for Gas Mixture Separation. Nature Communications 2018, 9, 1–11.

(3) Zhao, J.; He, G.; Huang, S.; Villalobos, L. F.; Dakhchoune, M.; Bassas, H.; Oveisi, E.; Agrawal, K. V. Etching Nanopores in Single-Layer Graphene with an Angstrom Precision for High-Performance Gas Separation. Science Advances 2019, 5, eaav1851.

(4) Huang, S.; Villalobos, L. F.; Li, S.; Babu, D. J., Vahdat, M. T., Oveisi E., Agrawal, K. V. High-permeance Single-Layer Graphene Membrane with A Molecular Sieving Resolution of 0.2 Å, Submitted.