Understanding Gas Transport Behavior through Few-Layer Graphene Oxide Membranes Controlled by Tortuosity and Interlayer Spacing.

Here, we elucidate the gas transport behavior through few-layer graphene oxide membranes (FGOMs) that have a systematically controlled diffusion pathway, including tortuosity and channel width. The obtained unusual gas permeation order (especially, CH4 > O2 > N2) of the FGOM provides strong evidence that gas molecules can indeed penetrate through the empty voids created by horizontally assembled GO, which allows selective gas transport features. These unique transport features of the FGOM originate from its continuously connected channel structure, which is an analogue of an ultrapermeable glassy polymer with extremely large free volumes in dense films. Furthermore, variation of the channel width in the range of 0.50-0.55 nm leads to notable changes in the gas permeance orders related to CH4, indicating that there is a transition region for switching the gas transport mechanism between a molecular sieving character and the solution-diffusion model.