Millisecond lattice gasification for high-density CO2- and O2-sieving nanopores in single-layer graphene

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Science Advances  24 Feb 2021:
Vol. 7, no. 9, eabf0116
DOI: 10.1126/sciadv.abf0116
  • Fig. 1 Precise incorporation of a high density of vacancy defects in graphene by millisecond gasification.

    (A) Schematic of the MGR setup. (B) Profile of the O3 pulse in MGR. (C) Raman spectroscopy analysis showing the evolution of the N-SLG with increasing O3 dose. (D and E) Scanning tunneling microscopy (STM) images of N-SLG on Cu foil prepared by MGR at 250°C. The sample was annealed at 900°C before the STM imaging. (F) The temperature-dependent coverage rate of the functional oxygen groups on N-SLG fitted with linear regression. In the x axis, R refers to the universal gas constant and T refers to the functionalization temperature. (G and H) STM images of highly oriented pyrolytic graphite (HOPG) treated by MGR at 250°C. (I) The height profile of the line (AA′) in (H). The images were acquired by transferring samples to STM immediately after MGR, and no further thermal annealing was carried out. STM images of samples shown in (G and H) after annealing at 800°C inside the STM chamber (J and K). (L) The height profile of the line (BB′) in (K). a.u., arbitrary units.

  • Fig. 2 AC-HRTEM–based analysis of the lattice structure of the vacancy defects incorporated in N-SLG from millisecond gasification.

    (A and B) AC-HRTEM images of the vacancy defects and corresponding lattice-fitted structures (dots indicate missing carbon atoms). The repeated occurrence of each defect within the set of images is indicated inside the bracket. For example, P-13i (×2) indicates that P-13i was observed two times. (C) Top: Distribution of the number of missing carbon atoms in the vacancy defects based on the AC-HRTEM. Bottom: The predicted distribution of the missing carbon atoms using the gasification kinetics model.

  • Fig. 3 Gas separation performance from the vacancy defects in N-SLG incorporated by the millisecond gasification.

    Evolution of the gas permeance (A) and extracted activation energies of H2, CO2, and CH4 for transport across N-SLG (B) as a function of the O3 dosage. (C) CO2/CH4 selectivity and CO2 permeance from N-SLG etched at 250°C (τ = 0.1 s) with varying td. (D) Comparison of the gas separation performance of N-SLG etched at 250° and 290°C and (E) the corresponding van der Waals gap extracted from HRTEM after heating the samples to 900°C (unfunctionalized pores). td was 0.5 s for the 250° and 290°C cases (using Ar purge) and 0.2 s for the optimized 290°C case (using the He purge). (F) Photograph of the centimeter-scale N-SLG membrane on the smoothened metal-mesh support. Red lines highlight the edges of the membrane. Photo credit: Shiqi Huang, École Polytechnique Fédérale de Lausanne.

  • Fig. 4 Gas separation performance of N-SLG prepared by MGR followed by in situ O2 treatment at 200°C.

    (A) CO2 and N2 evolution in the permeate side during the in situ etching. (B) Gas permeance at 25°C as a function of the kinetic diameter from the as-prepared N-SLG membrane, from those subjected to the in situ O2 treatment, and from that subjected to O3 at 25°C for 2 min. The term “repeat” refers to repeating the in situ O2 treatment after 2 days of gas permeance testing. (C) Comparison of the gas pair selectivity data at 25°C of the as-prepared N-SLG membrane with those subjected to the in situ O2 treatment. (D) Comparison of the CO2/N2 mixture separation performance from the membranes prepared in this study with the state-of-the-art membranes for postcombustion capture. The target area refers to the membrane performance needed to surpass the energy efficiency of the amine-based absorption process (6, 7). MMPs, metal-induced ordered microporous polymers.

Supplementary Materials

  • Supplementary Materials

    Millisecond lattice gasification for high-density CO2- and O2-sieving nanopores in single-layer graphene

    Shiqi Huang, Shaoxian Li, Luis Francisco Villalobos, Mostapha Dakhchoune, Marina Micari, Deepu J. Babu, Mohammad Tohidi Vahdat, Mounir Mensi, Emad Oveisi, Kumar Varoon Agrawal

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