Hydrogen is a promising energy source for the low-carbon economy but light-weight materials with excellent gas barrier properties are needed for its transport and storage. Nanocomposites can deliver such properties, using two-dimensional materials to provide a barrier within the polymer matrix. Herein, we have investigated the optimal characteristics of graphene-based fillers for their use as a hydrogen barrier in a polymer matrix. We employed reduced graphene oxide (rGO) and graphene nanoplatelets (GNPs) that presented distinct filler morphologies and melt-mixed them separately into isotactic polypropylene (PP). A reliable characterisation approach was developed to evaluate the effective aspect ratio of 2D nanomaterials within a polymer matrix by combining BET surface area for the effective thickness and microscopic measurement for lateral size on the microstructure of the nanocomposite samples. The effective aspect ratio values were evaluated to be 153 ± 85 for the rGO and 14 ± 6 the GNPs. Therefore, the rGO outperformed the GNPs in improving both the mechanical and H barrier properties of their nanocomposites. The modulus of PP was increased from 1.2 GPa to 2.3 GPa by the addition of 0.9 vol% of the rGO, whereas GNP-filled PP only reached 1.8 GPa by the addition of a higher loading of the GNP (4.6 vol%). The H permeability of PP-rGO nanocomposites compared to pure PP was reduced by 40% at 0.9 vol% loading, compared to PP-GNP samples which had a 30% reduction at 4.6 vol% loading. Nielson's model was employed to analyse the results, showing an effective aspect ratio of rGO and GNP to be 165 and 20 respectively, consistent with the characterisation results.

中文翻译：

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新一代轻质储氢用石墨烯/聚丙烯纳米复合材料气阻改善机制

氢是低碳经济的一种有前途的能源，但其运输和储存需要具有优异气体阻隔性能的轻质材料。纳米复合材料可以通过使用二维材料在聚合物基质内提供屏障来提供此类特性。在此，我们研究了石墨烯基填料在聚合物基体中用作氢屏障的最佳特性。我们采用还原氧化石墨烯（rGO）和石墨烯纳米片（GNP），它们具有不同的填料形态，并将它们分别熔融混合成等规聚丙烯（PP）。我们开发了一种可靠的表征方法，通过结合有效厚度的 BET 表面积和纳米复合材料样品微观结构横向尺寸的显微测量来评估聚合物基体中二维纳米材料的有效长宽比。rGO 的有效长宽比值为 153 ± 85，GNP 的有效长宽比值为 14 ± 6。因此，rGO 在改善纳米复合材料的机械性能和 H 阻隔性能方面优于 GNP。通过添加 0.9 vol% 的 rGO，PP 的模量从 1.2 GPa 增加到 2.3 GPa，而通过添加更高负载量的 GNP（4.6 vol%），GNP 填充的 PP 仅达到 1.8 GPa。与纯 PP 相比，PP-rGO 纳米复合材料的 H 渗透率在 0.9 vol% 负载量下降低了 40%，而 PP-GNP 样品在 4.6 vol% 负载量下 H 渗透率降低了 30%。采用Nielson模型对结果进行分析，显示rGO和GNP的有效长宽比分别为165和20，与表征结果一致。