Perfect proton selectivity in ion transport through two-dimensional crystals

Lucas Mogg, Sheng Zhang, Guang Ping Hao, Gopinadhan Kalon, Donnchadh Barry, B L Liu, H M Cheng, Andre Geim, M Lozada-Hidalgo

Research output: Contribution to journalArticlepeer-review


Recent experiments have shown that defect-free monolayers of graphene and hexagonal boron nitride (hBN) are surprisingly permeable to thermal protons despite the two-dimensional (2D) materials are completely impenetrable to all gases. Even individual atomic-scale defects such as, e.g., vacancies caused notable permeation of small atoms and molecules and could be detected. However, it remains untested whether or not small ions can permeate through pristine 2D crystals. Here we show that mechanically-exfoliated graphene and hBN exhibit perfect Nernst selectivity: Only protons can permeate through these crystals, with no detectable flow of counterions. Using electrical measurements, we studied ion transport through suspended 2D membranes that had few if any atomic-scale defects as shown by gas permeation tests. The 2D crystals were then used to separate reservoirs filled with hydrochloric acid solutions. Protons accounted for all the detected current with chloride ions being blocked. These results corroborate the previous conclusion that only thermal protons are able to pierce defect-free 2D crystals. Besides the fundamental importance for understanding of the mechanism of proton transport through atomically-thin crystals, our results are also of interest for research on various separation technologies based on 2D materials.
Original languageEnglish
JournalNature Communications
Publication statusPublished - 18 Sept 2019

Research Beacons, Institutes and Platforms

  • National Graphene Institute


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