Moulod Mohammad, Moghaddam Saeed
Mechanical and Aerospace Engineering Department, University of Florida, Gainesville, FL, USA.
Mol Simul. 2022;48(7):621-630. doi: 10.1080/08927022.2022.2042529. Epub 2022 Feb 28.
Understanding the nature of water transport in nanoscale is of high importance. Graphene properties such as mass flow rate, stability, filtration efficiency, and selectivity have been studied in various fields. It is a widely held view that the hydrophilicity of graphene oxide enhances the water transport properties. In this study, it is shown that despite this belief, a combination of graphene and graphene oxide can yield superior transport properties including high mass flow rate and directionality. Firstly, different membrane characteristics such as the smallest pore diameter for water molecules sieving and mass flow rate have been evaluated. Furthermore, a combination of graphene and graphene oxide, a biphilic stack of hydrophobic and hydrophilic layers, are used to evaluate the mass flow rates and results are compared with that of normal graphene oxide laminates. The proposed structure acts like a water diode i.e. conduct water molecules in a desired direction and increases the mass flow rate several times. The effect of interatomic potential, oxidation level and charge, and the spacing between layers on both mass flow rate and directionality are examined. It is found that an optimized structure conducts water in a desired direction and increases the mass flow rate up to 10 times for the small interlayer distance of 7 Å compared to the normal graphene oxide laminates. The given structures can be used in a wide range of filtration applications where selective water sieving with high mass flow rate is desired.
了解纳米尺度下水的传输性质至关重要。氧化石墨烯的质量流率、稳定性、过滤效率和选择性等性质已在各个领域得到研究。人们普遍认为氧化石墨烯的亲水性增强了水的传输性质。在本研究中，结果表明，尽管有这种观点，但石墨烯与氧化石墨烯的组合能产生优异的传输性质，包括高质量流率和方向性。首先，评估了不同的膜特性，如水分子筛分的最小孔径和质量流率。此外，使用石墨烯与氧化石墨烯的组合，即疏水层和亲水层的双亲性堆叠，来评估质量流率，并将结果与普通氧化石墨烯层压板的结果进行比较。所提出的结构就像一个水二极管，即能使水分子沿所需方向传导，并将质量流率提高数倍。研究了原子间势、氧化水平和电荷以及层间距对质量流率和方向性的影响。结果发现，与普通氧化石墨烯层压板相比，对于7 Å的小层间距，优化后的结构能使水沿所需方向传导，并将质量流率提高多达10倍。所给出的结构可用于广泛的过滤应用中，这些应用需要具有高质量流率的选择性水筛分。
