Fabrication, Pressure Testing, and Nanopore Formation of Single Layer Graphene Membranes

Single-layer graphene (SLG) membranes have great promise as ultrahigh flux, high selectivity membranes for gas mixture separations due to their single atom thickness. It remains a central question whether SLG membranes of a requisite area can exist under an imposed pressure drop and temperatures needed for industrial gas separation. An additional challenge is the development of techniques to perforate or otherwise control the porosity in graphene membranes to impart molecularly sized pores, the size regime predicted to produce high gas separation factors. Herein, we report fabrication, pressure testing, temperature cycling, and gas permeance measurements through free-standing, low defect density SLG membranes. Our measurements demonstrate the remarkable If chemical and mechanical stability of these 5,rim diameter suspended SLG membranes, which remain intact over weeks of testing at pressure differentials of >0.5 bar, repeated temperature cycling from 25 to 200 degrees C, and exposure to 15 mol % ozone for up to 3 min. These membranes act as molecularly impermeable barriers, with very low or near negligible background permeance. We also demonstrate a 1077 degrees C temperature O-2 etching technique to create nanopores on the order of similar to 1 nm diameter as imaged by scanning tunneling microscopy, although transport through such pores has not yet been successfully measured. Overall, these results represent an important advancement that will enable graphene gas separation membranes to be fabricated, tested, and modified in situ while maintaining remarkable mechanical and thermal stability.