Graphene and graphene oxide (GO) have significant potential as nanosheets in many applications, including energy storage, sensors, barriers, fuel cells, and flexible electronics. Recently, GO membranes have been considered as molecular filters to separate ions as well as gases. Recently we reported few-layered GO films, supported by microporous polymeric membrane, can be used for selective CO2 separation from flue gases. GO can be easily obtained from chemical exfoliation of graphite, and mass production is also available. Because GO is hydrophilic, it is highly dispersible in aqueous solution. It can therefore be coated by using existing coating methods, such as spin-casting, spraying, vacuum filtration, and direct evaporation. A key idea to employ two-dimensional GO sheets as membranes is to generate slit-like pores, as it is not the case for typical pores in most polymeric membranes. The interplanar spacing of stacked GO membranes ranges from 0.6 to 1.0 nm, depending on the stacking manner and the amount of intercalated water molecules. That is, small gases or water molecules can travel through the spacing between GO sheets. However, since GO sheets have a high aspect ratio and layered structures, the GO size and stacked GO thickness should be carefully considered to reduce high diffusional tortuosity, which leads to high gas permeability. In this study, we prepared ultrathin GO membranes on a polyethersulfone (PES) microporous support membrane by spin-casting or spraying of fully exfoliated GO solution. When GO sheets were well-stacked (highly interlocked as a brick model) without any defect, such GO thin-film composite (TFC) membranes showed high CO2 permeance with high CO2/gases selectivities. Moreover, the CO2 separation performances were much more enhanced by the presence of water molecules in the feed. In this work, the outstanding CO2 separation character of GO TFC membranes will be discussed in detail by showing inherent CO2-philic nature of GO sheets.

CO2-philic graphene oxide thin film composite membranes

249th National Meeting (2015)

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