In a proton-exchange membrane fuel cell, the proton-exchange membrane is located between the oxidant and the fuel, which facilitates proton conduction and prevents the penetration of gas molecules. In this study, sulfonated graphene oxides (SG) were synthesized, and a series of SG/Nafion composite multilayer membranes were prepared using layer-by-layer assembling. This multilayer membrane-structure has an efficient orientation effect on the SG sheets. The thinner the layer is, the more significant is the orientation effect. A statistical angle between the SG sheets and the membrane surface ($\Theta$) is used to represent the orientation of SG sheets, and a correlation between the thickness of the layers and $\Theta$ is found. Under various conditions, these multilayer composite membranes improve the gas-barrier properties (H${}_2$, O${}_2$, and water vapor) and proton conductivity. The effect of $\Theta$ on the gas-barrier properties and proton conductivity of the membranes is discussed. Our results reveal that the SG sheets have excellent gas-barrier properties in the longitudinal direction and good proton conductivity in the lateral direction. Furthermore, based on positron-annihilation lifetime spectroscopy, it is found that the diffusion coefficients of gas molecules in all the SG/Nafion composite membranes are almost identical. In other words, the orientation of the SG sheets changes the gas-barrier properties of the membranes by altering the morphology of the diffusion paths for the gas molecules during the permeation.

在质子交换膜燃料电池中，质子交换膜位于氧化剂和燃料之间，这有利于质子传导并防止气体分子渗透。本研究合成了磺化氧化石墨烯（SG），并通过逐层组装制备了一系列SG / Nafion复合多层膜。该多层膜结构对SG片材具有有效的取向效果。层越薄，取向效果越显着。SG片和膜表面之间的统计角度（$\Theta$）用来表示SG片材的方向以及各层厚度与 $\Theta$被发现。这些多层复合膜可在各种条件下改善阻气性（H${}_2$O${}_2$，以及水蒸气）和质子传导性。的效果$\Theta$讨论了膜的阻气性和质子传导性。我们的结果表明，SG片材在纵向方向上具有出色的阻气性，在横向方向上具有良好的质子传导性。此外，基于正电子-没寿命谱，发现所有SG / Nafion复合膜中气体分子的扩散系数几乎相同。换句话说，SG片材的取向通过改变渗透过程中气体分子的扩散路径的形态来改变膜的气体阻隔性。