Graphene oxide (GO) based multi-layered membranes have shown outstanding molecular-sieving properties for gas separation, surpassing the upper bound for polymeric membranes especially for hydrogen decarbonization. At the same time, the mechanism of gas permeation through such 2D GO membranes is very different in comparison to the traditional polymeric membranes due to multilayer, laminated nature of the former. For strategical design of novel membranes based on two-dimensional materials, it is important to understand the mechanism and to be able to measure two key parameters for gas transport: diffusivity and solubility. Such measurements are well established for the characterization of transport properties of bulk polymeric membranes. However, it is still a challenge to measure gas diffusion coefficients directly and accurately in ultra-thin multi-layered membranes. The lack of characterization limits our understanding of the mechanisms of gas transport though such membranes. In this work, we applied a time-lag method to determine the diffusivities for He, H₂, O₂, N₂, CH₄, CO₂ and H₂/CO₂ equimolar mixture by on-line mass spectrometry. In contrast to polymeric membranes, the diffusivity and diffusion activation energy for all gases in 2D membranes are exponentially dependent on pathway length. Thus, in 2D membrane we can use an easy strategy to precisely regulate permeability and selectivity by the adjustment of the number of nanolayers and the size of 2D flakes, which is not possible using traditional polymeric membranes. This study is important for both the characterization and the standardization of gas transport properties of multi-layered membranes, and the design of novel membranes based on 2D materials.

基于氧化石墨烯 (GO) 的多层膜在气体分离方面表现出出色的分子筛性能，超过了聚合物膜的上限，尤其是在氢气脱碳方面。同时，由于前者的多层、层压性质，与传统的聚合物膜相比，这种 2D GO 膜的气体渗透机制非常不同。对于基于二维材料的新型膜的战略设计，重要的是了解其机理并能够测量气体传输的两个关键参数：扩散率和溶解度。这种测量已经很好地用于表征本体聚合物膜的传输特性。然而，在超薄多层膜中直接准确地测量气体扩散系数仍然是一个挑战。缺乏表征限制了我们对通过此类膜的气体传输机制的理解。在这项工作中，我们应用时滞法来确定 He、H 的扩散率₂、O ₂、N ₂、CH ₄、CO ₂和H ₂ /CO ₂等摩尔混合物的在线质谱分析。与聚合物膜相反，二维膜中所有气体的扩散率和扩散活化能都以指数方式依赖于通路长度。因此，在二维膜中，我们可以使用一种简单的策略通过调整纳米层的数量和二维薄片的大小来精确调节渗透性和选择性，这在使用传统聚合物膜时是不可能的。这项研究对于多层膜气体传输特性的表征和标准化，以及基于二维材料的新型膜的设计都很重要。