High-Performance Gas Separation Membranes by Guided-Assembly of Graphene-based Nanocomposites

我们在这个项目中的研究成果有三个方面。首先，我们发现GO-聚阳离子复合物凝结太快而不能得到均匀的浆料，因此不能得到无缺陷的气体分离膜。在高GO-聚阳离子负载（高浓度），我们可以获得保形涂层与杆/叶片涂层方法。但是所得到的膜变得太厚，但由于快速聚集，仍然经常有缺陷。我们可以使用非聚电解质（如氢键聚合物）生产更光滑的涂层，但仍然观察到只有低氢选择性。然而，当我们使用带正电的纳米颗粒和真空过滤时，我们实现了共形和无缺陷的膜，产生高达150的选择性和高达约4000 GPU的渗透率。基于用无聚合物的纳米片分散体进行的实验，我们还发现真空过滤可用于压实通过其他涂覆方法（例如喷涂）制备的膜。总之，这项合作研究导致了四个基本概念的建立：（1）静电相互作用在稳定GO基膜方面非常有效;（2）引导组装方法（如真空辅助过滤和真空喷涂）应进行优化，以实现无缺陷膜;（3）复合膜应该不含聚合物或富含纳米片，以开发具有高氢选择性的无缺陷膜。

Our research achievements in this project are threefold. First, we have found that the GO-polycation composites coagulate too fast to give uniform slurries and, thus, defect-free gas separation membranes. At high GO-polycation loadings (high concentrations), we could obtain conformal coatings with rod/blade-coating methods. But the resulting membranes became too thick but were still often defective because of fast aggregation. We could produce smoother coatings using non-polyelectrolytes (such as hydrogen-bondable polymers) but still observed only low hydrogen selectivity. However, when we used positively charged nanoparticles and vacuum filtration, we achieved conformal and defect-free membranes, yielding selectivities up to 150 and permeabilities up to around 4000 GPU. Based on the experiments made with polymer-free nanosheet dispersions, we also found that vacuum filtration can be used for compacting membranes that are prepared by other coating methods such as spray-coating. Overall, this collaborative research resulted in the establishment of four fundamental notions: (1) Electrostatic interactions are highly effective in stabilizing GO-based membranes; (2) guided-assembly methods (such as vacuum-assisted filtration and vacuum-spray-coating) should be optimized for achieving defect-free membranes; (3) composite membranes should be polymer-free or rich in nanosheets for developing defect-free membranes with high hydrogen selectivity.