Unveiling the interlayers and edges predominant controlling transport pathways in laminar graphene oxide membranes via different assembly strategies

Abstract

There is an ongoing enthusiasm in laminar graphene oxide (GO) membranes owing to their great potentials for high-precise separation applications. However, the diametrically different permselectivity properties of reported laminar GO membranes via diverse assembly strategies are poorly understood. Our knowledge about process-structure-performance relationships of laminar GO membranes remain fragmental. Herein, spin-coated and filtrated GO membranes were prepared, which formed interlayers and edges predominant controlling transport pathways under horizontal and vertical assembly force fields respectively. It is demonstrated that the interlayers predominant controlling transport pathways in the spin-coated GO membranes allow hydrated ions slipping across the interlayer channels with low friction, and the EDTA cross-linking restricts the interlayer spacing to enhance the size sieving effect. The s-GO-EDTA membrane delivered monovalent ion permeance of ∼ 0.269 mol m−2 h−1 with mono/divalent ion selectivity of ∼ 7.3. While the edges predominant controlling transport pathways in the filtrated GO membranes provide functional groups at edges to interact with hydrated ions, and the EDTA cross-linking brings more functional groups to reinforce the wall affinity effect. The f-GO-EDTA membrane achieved monovalent ion permeance of ∼ 0.686 mol m−2 h−1 with mono/divalent ion selectivity of ∼ 10.3. The two pathways models correlated with ion permeation performances explicate that hydrated ions diffusion fundamentally obeys the hydrodynamic flow behaviors strongly controlled by channel size, path length and ion-wall interactions. These findings have extensive implications of designing transport pathways of laminar GO membranes, as well as understanding transport mechanisms of hydrated ions in nanoconfined channels.