Insight from perfectly selective and ultrafast proton transport through anhydrous asymmetrical graphene oxide membranes under Grotthuss mechanism

M Zakertabrizi and E Hosseini and AH Korayem and A Razmjou and AG Fane and V Chen, JOURNAL OF MEMBRANE SCIENCE, 618, 118735 (2021).

DOI: 10.1016/j.memsci.2020.118735

Protons transport profoundly affects diverse fields from proton-exchange membrane fuel cells to storing liquid hydrogen. Recent advances have extended proton-exclusive transport to the two-dimensional channels that use hydrous mechanisms for fast proton transport, where the main challenge is the limited selectivity. However, the physical and chemical properties of 2D nanosheets like GO have the potential to implement full selective and ultrafast proton transport. Here, we uncover the physical potential of anhydrous proton transfer mechanism inside two-dimensional space between graphene nanosheets to exploit the exceptional full proton-selective ability and ultrafast conveyance speed of the Grotthuss mechanism. Reactive molecular dynamics simulations illustrate that the interlayer space between two graphene oxide nanosheets, carpeted with hydroxyl functional groups as additional hopping stages to enable the Grotthuss mechanism, can convey protons without water. Further, we dissect three essential factors that provide a deeper insight into ultrafast proton transport: (i) transitional phase to full anhydrous transport, (ii) outlet size for containing undesired species, and (iii) elastic behavior of the membranes under external strain. Our results show that changes in surface geometry can dramatically increase the diffusion rate in the presence of a small electric field by similar to 70% compared to hydrous transport. These findings can be used not only to guide the efforts in manufacturing a new generation of sustainable nanochannels but also to advance the pioneering technologies revolving around hydrogen.

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