Facile Synthesis of Large-Area Atomically Thin Graphene Membranes via Isopropanol-Assisted Hot Lamination

Nanoporous atomically thin graphene membrane has been considered as an ideal candidate for next-generation membrane-based technologies. To realize this membrane applications, scalable graphene synthesis and facile large-area membrane fabrication are imperative. While catalytic chemical vapor deposition (CVD) has been demonstrated to be an economical and versatile way to enable the commercial production of high-quality graphene, CVD graphene has to be transferred from the growth substrate onto a porous support substrate to provide mechanical stability for membrane applications. However, commonly used polymer scaffold methods typically leave polymer residues detrimental to membrane performance, while transfers without sacrificial polymers suffer from low transfer yield leading to high membrane leakage. Hence, high-yield transfer of clean large-area graphene onto appropriately porous supports (without compromising support porosity/integrity) using scalable processes for membrane applications remains challenging. In this work, we systematically investigate the factors influencing the transfer of CVD graphene from a Cu foil onto a model polycarbonate track etch (PCTE) support for fabricating large-area atomically thin membranes via manual compression, mechanical press and scalable lamination approaches. Particularly, we report on a novel roll-to-roll manufacturing compatible isopropanol-assisted hot lamination that allows for facile, clean and scalable transfer of centimeter-scale graphene onto model PCTE supports with coverage ≥ 99.2% without compromising support porosity, which is one of the best values reported to this date for centimeter-scale atomically thin membranes. The remaining 0.8% of leakage is attributed to defects (>50 nm) primarily along wrinkles formed during CVD growth. Furthermore, water-assisted oxidation effectively detaches CVD graphene from the Cu foil and helps graphene transfer, but significantly damages (~10%) graphene along wrinkles. Finally, fully functional centimeter-scale atomically thin membranes are demonstrated.