Futamura Ryusuke, Iiyama Taku, Ueda Takahiro, Bonnaud Patrick A, Coudert François-Xavier, Furuse Ayumi, Tanaka Hideki, Pellenq Roland J-M, Kaneko Katsumi
Department of Chemistry, Faculty of Science, Shinshu University, 3-1-1, Asahi, Matsumoto, 390-8621, Japan.
Research Initiative for Supra-Materials, Shinshu University, 4-17-1, Wakasato, Nagano, 380-8553, Japan.
Nat Commun. 2024 Apr 27;15(1):3585. doi: 10.1038/s41467-024-47838-9.
Graphene oxide (GO) is the one of the most promising family of materials as atomically thin membranes for water-related molecular separation technologies due to its amphipathic nature and layered structure. Here, we show important aspects of GO on water adsorption from molecular dynamics (MD) simulations, in-situ X-ray diffraction (XRD) measurements, and ex-situ nuclear magnetic resonance (NMR) measurements. Although the MD simulations for GO and the reduced GO models revealed that the flexibility of the interlayer spacing could be attributed to the oxygen-functional groups of GO, the ultra-large GO model cannot well explain the observed swelling of GO from XRD experiments. Our MD simulations propose a realistic GO interlayer structure constructed by staggered stacking of flexible GO sheets, which can explain very well the swelling nature upon water adsorption. The transmission electron microscopic (TEM) observation also supports the non-regular staggered stacking structure of GO. Furthermore, we demonstrate the existence of the two distinct types of adsorbed water molecules in the staggered stacking: water bonded with hydrophilic functional groups and "free" mobile water. Finally, we show that the staggered stacking of GO plays a crucial role in H/D isotopic recognition in water adsorption, as well as the high mobility of water molecules.
氧化石墨烯（GO）因其两亲性和层状结构，作为用于水相关分子分离技术的原子级薄膜材料，是最具前景的材料家族之一。在此，我们通过分子动力学（MD）模拟、原位X射线衍射（XRD）测量和非原位核磁共振（NMR）测量，展示了氧化石墨烯在水吸附方面的重要特性。尽管对氧化石墨烯和还原氧化石墨烯模型的分子动力学模拟表明，层间距的灵活性可归因于氧化石墨烯的氧官能团，但超大氧化石墨烯模型无法很好地解释X射线衍射实验中观察到的氧化石墨烯膨胀现象。我们的分子动力学模拟提出了一种由柔性氧化石墨烯片交错堆叠构成的现实的氧化石墨烯层间结构，它能很好地解释水吸附时的膨胀特性。透射电子显微镜（TEM）观察也支持氧化石墨烯的不规则交错堆叠结构。此外，我们证明在交错堆叠中存在两种不同类型的吸附水分子：与亲水性官能团结合的水和“自由”移动水。最后，我们表明氧化石墨烯的交错堆叠在水吸附中的H/D同位素识别以及水分子的高迁移率方面起着关键作用。
