(662g) Rapid Growth of Nanocrystalline Single-Layer Porous Graphene for Gas Separation

Single-layer porous graphene is highly attractive as the selective layer in membrane-based gas separation due to its exceptional mechanical strength, chemical stability, and atomic thickness, which allows for high permselective flux. Current approaches to fabricate porous graphene membranes involve synthesizing graphene films followed by post-synthetic treatments to introduce porosity through chemical or physical techniques, adding complexity and limiting scalability. Direct synthesis of porous graphene in a single step is therefore highly desirable to streamline membrane fabrication and enhance scalability.

In this work, we demonstrate the direct synthesis of nanocrystalline single-layer porous graphene using low-pressure chemical vapor deposition (LPCVD). By systematically tuning the growth temperature, growt time and methane-to-hydrogen ratio, we identified a low-temperature growth regime (~720 °C) that enables the formation of continuous, unfragmented graphene films with a high density of hydrogen-permeable vacancy defects. The resulting graphene films are nanocrystalline, consisting of misoriented grains only a few nanometers in size. Imperfect stitching between grains generates grain-boundary defects with 10 or more missing carbon atoms, forming sub-nanometer pores that selectively transport hydrogen.[1]

As confirmed by aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM), the centimeter-scale graphene membranes feature pores smaller than 0.55 nm, consistent with extremely high H₂/SF₆ selectivity exceeding 2000 and H₂ permeance above 1000 GPU. This direct synthesis method represents a scalable and energy-efficient approach for fabricating high-performance gas separation membranes, with significant implications for hydrogen purification and industrial gas processing.

References

[1] C. Kocaman, L. Bondaz, M. Rezaei, J. Hao, and K. V. Agrawal, “Direct synthesis of nanocrystalline single-layer porous graphene for hydrogen sieving,” Carbon, vol. 221, Mar. 2024, doi: 10.1016/j.carbon.2024.118866.