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，我们发现氧化石墨烯多阳离子复合材料凝结太快，无法形成均匀的浆液，因此无法形成无缺陷的气体分离膜。在高氧化石墨烯多阳离子负载（高浓度）下，我们可以用棒/叶片涂层方法获得保形涂层。但最终的膜变得太厚，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，但仍然只观察到低氢选择性。然而，当我们使用带正电的纳米颗粒和真空过滤时，我们获得了适形和无缺陷的膜，其选择性高达150，渗透率高达4000 GPU左右。在无聚合物纳米片分散体的实验基础上，我们还发现真空过滤可以用于通过喷涂等其他涂层方法制备的膜的压实。总的来说，这项合作研究建立了四个基本概念：(1)静电相互作用在稳定氧化石墨烯基膜方面非常有效；(2)应优化导向装配方法（如真空辅助过滤和真空喷涂），以实现膜的无缺陷；(3)复合膜应不含聚合物或富含纳米片，以发展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.