Invariance of Water Permeance through Size-Differentiated Graphene Oxide Laminates
Invariance of Water Permeance through Size-Differentiated Graphene Oxide Laminates
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DOI：
10.1021/acsnano.8b02015
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发表时间：
2018-08-01
期刊：
影响因子：
17.1
通讯作者：
Arnold, Michael S.
中科院分区：
文献类型：
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作者：
Saraswat, Vivek;Jacobberger, Robert M.;Arnold, Michael S.
由氧化石墨烯纳米片制成的层压板已被证明具有高透水性和防盐性，因此，由于其在分离应用中的潜力，引起了科学界的极大兴趣。然而，关于水通过这种层压板的输送途径尚无明确的共识。在这项研究中，我们合成了化学上相同的氧化石墨烯纳米片，其横向尺寸相差2个数量级，并通过压力辅助沉积这些纳米片制备的不同厚度的层压板测量了水的渗透率。我们的研究结果表明，尽管这些层压板的横向尺寸差异如此之大，但通过这些层压板的透水性几乎是相同的。此外，我们使用一个相互连接的纳米通道网络模型来模拟流体在层压板中的流动，以便与实验进行比较。与实验数据相结合的模拟表明，不太可能像某些研究中提出的那样，主要的流体输送途径是围绕单个薄片的迂回的横向通道。相反，非理想因素，包括通过薄片内部针孔缺陷的反薄片流动和/或层压板中不完美堆积引起的流过区域，可以显著影响流体的输送途径。这种非理想性的存在也得到了厚度和时间相关的渗透率测量和红外光谱的支持，这表明水在层压板中主要采用块状结构。这些分析是理解水通过氧化石墨烯层压板的重要一步，并进一步了解这些材料内部的水结构，这可能在下一代分离应用中具有巨大的潜力。
Laminates made of graphene oxide nanosheets have been shown to exhibit high water permeance and salt rejection and, therefore, have generated immense interest from the scientific community due to their potential in separation applications. However, there is no clear consensus on the water-transport pathways through such laminates. In this study, we synthesized chemically identical graphene oxide nanosheets with 2 orders of magnitude difference in lateral sizes and measured water permeance through laminates of different thicknesses fabricated by pressure assisted deposition of these nanosheets. Our results reveal that water permeance through these laminates is nearly the same despite such massive difference in lateral sheet size. Furthermore, we simulated fluid flow through laminates using an interconnected nanochannel network model for comparison with experiments.. The simulations in combination with the experimental data show that it is unlikely that the dominant fluid transport pathway is a circuitous, lateral pathway around individual sheets, as has been proposed in some studies. Rather, nonideal factors including trans-sheet flow through pinhole defects in sheet interiors and/or flow-through regions arising from imperfect stacking in the laminates can significantly affect the fluid transport pathways. The presence of such nonidealities is also supported by thickness- and time-dependent measurements of permeance and by infrared spectroscopy, which indicates that water predominantly adopts a bulk-like structure in the laminates. These analyses are significant steps toward understanding water transport through graphene oxide laminates and provide further insight toward the structure of water inside these materials, which could have immense potential in next-generation separation applications.