(635e) Water Permeation through Structural Defects of Single-Layered Graphene Oxide Membranes

Comparing with traditional methods, membrane-based water treatment technologies are essential due to the low energy consumption and high efficiency in removing contaminants or salts. As the flux cross the membrane decreases with membrane thickness, to balance the pay off between permeability and selectivity, membrane should possess pores large enough to allow the passage of water molecules but small enough to block the large solutes, and the membrane thickness should be as thin as possible to provide high flux, which makes the “ideal” membrane might be in the form of one atomic thickness and with suitable pores. Materials like graphene and its derivatives just meet this requirement and have been considered as a promising candidate to prepare ultrathin membranes which mostly closing to the “ideal” state. However, the harsh conditions to prepare macroscopic single-layer graphene with sufficient densities and size controllable pores have hindered its practical applications. Herein, by clarifying two distinct water transportation mechanisms for membranes with sub-monolayer and multilayer GO coverage, a methodology to fabricate nominal single-layered GO membrane was proposed for the first time. The Water flux exhibited a transition from linear to exponential decrease as the GO coverage increase, the condition to prepare nominal single-layered GO membrane could be extrapolated from the turning point of the transition, the as-fabricated membrane which with thickness closing to one-carbon-atom exhibits high water permeance around 64 L·m^-2·h^-1·bar^-1, and defects on GO flakes provide major contribution for the membrane sieving property. By evaluating the separation performance of this membrane with rigid molecules, the effective defect size of GO was determined to be ~1.2-1.7 nm. This membrane with nominal single-layer GO cover also show great potential in protein separation.