氧化石墨烯膜层间纳米通道网络的性质和其对筛选过滤影响的研究

Graphene-derived membranes have attracted much interest recently due to their high-efficiency, energy-saving, and highly-selective properties. The properties of filtration and selection of grapenene oxide membranes are determined by the properties of the network structures formed by the different nano-channels between the layers of the membranes. However, due to spacial (nano-scale) constraint and the effects of the structural complexity of grapenene oxide (density and distribution of the surface oxidized-groups, defects, and wrinkles etc.), it is formidable to explore the overall network structures of the nano-channels experimentally. Therefore, there is still a lack of microscopic understanding on the filtration and separation properties as well as the methods of controlling them in grapheme oxide membranes. To overcome this difficulty, in this project, we propose to study the filtration and separation properties of graphene oxide membranes using a multiscale molecular dynamic simulation method combining all-atom and coarse-grained molecular dynamics simulations. This research will mainly focus on: (1) transport properties of molecules and ions in different nano-channels; (2) influences of the nano-channel network structures on the filtration and separation properties; (3) proposing schemes of structural optimization for different molecule separations. The obtained results, which can be generalized to other two-dimensional filtration materials, would find applications in water-cleaning, desalination of sea water, and fabrication of clean-energy materials, etc.

石墨烯衍生物薄膜由于其在渗透和分子、离子过滤方面表现出高效、节能和选择性强等特点引起了研究者的关注。氧化石墨烯膜的渗透、筛选过滤性取决于其层间由不同纳米通道组成的通道网络的性质。然而，实验上由于受到空间（纳米尺度）限制和氧化石墨烯结构复杂性（表面含氧基团密度和分布、缺陷和褶皱等多重因素）的影响，难以对整体的通道网络结构进行描述。这些原因导致对氧化石墨烯膜的筛选过滤性以及其调控的微观理解还比较缺乏。针对这一问题，本项目拟采用结合全原子和粗粒化的多尺度分子动力学模拟方法对氧化石墨烯膜的过滤性进行研究。主要研究目标为：（1）计算分子和离子在不同类型纳米通道中输运的物理性质；（2）通道网络结构的调控和对筛选过滤性的影响；（3）针对不同分子过滤提出结构优化设计方案。所得研究结果可以推广至其它二维体系过滤材料，应用于水净化、海水淡化和清洁能源制备等领域。

氧化石墨烯膜由于具备天然的纳米通道，可以用去过滤分离气体、离子和大分子。本项目主要确认了不同通道类型对于气体、离子和大分子输运的贡献，并结合固气、固液界面相互作用强度，设计气体、水合离子和大分子的筛选分离。如气体分子，主要通过贯穿氧化石墨烯膜的纳米孔来输运；水分子和水合离子通过贯穿孔以及层间输运；大分子通过较大的褶皱和人为构造的贯穿孔来通过。本项目通过沉降法，获得了氧化石墨烯膜上纳米通道的数量、大小和分布以及膜厚度与形成膜的氧化石墨烯片的大小的关系。因此确定了上述不同通道的数量以及分布。此外，在本项目中还通过裁剪石墨烯形成较大的孔来改变纳米通道的分布，使得氧化石墨烯的过滤性具有更大的可控性。本项目开展期间，和北京航天五院总装备部进行合作，目前研究结果可以应用于载人航天器气体密闭性检测。