基于原子分子动力学模拟的聚烯烃基阴离子交换膜氢氧根输运与力学性能研究
Hydroxide Transport and Mechanical Properties of Polyolefin-Based Anion Exchange Membranes from Atomistic Molecular Dynamics Simulations
AI总结：
本研究通过原子分子动力学模拟探究聚烯烃基阴离子交换膜的氢氧根输运与力学性能，揭示构效关系与二者的权衡，为高效筛选新型膜材料提供分子层面的依据。
摘要：
阴离子交换膜应用于碱性燃料电池，是成本更高的质子交换膜燃料电池的极具潜力的替代方案。然而，阴离子交换膜中的氢氧根离子电导率较低，目前研究人员仍在寻找兼具优异离子电导率、力学强度和化学稳定性的膜材料。本研究采用经典分子动力学模拟，研究了八种不同水合聚烯烃基膜的氢氧根离子输运行为与力学性能，以从分子层面理解这些体系的构效关系。我们分析了膜的微观结构，发现空腔尺寸分布较窄的聚合物中，水分子在氢氧根离子周围的堆积更紧密。我们估算了水分子与氢氧根离子的自扩散系数，发现在所有体系中水分子的扩散速率均高于氢氧根离子。氢氧根扩散的变化趋势与实验测得的电导率结果高度吻合。水会促进氢氧根的扩散，这一点在对相同化学组成的聚合物改变水合度时可被清晰观测到。在空腔较窄、氢氧根离子结合紧密的体系中，氢氧根的扩散速率最低，凸显了水通道对氢氧根输运的促进作用。最后，我们通过单轴形变计算了这些体系的力学性能，发现水合度更高的聚合物力学性能更差。原子分子动力学模型能够准确捕捉阴离子交换膜中氢氧根输运与力学性能之间的权衡关系，助力我们更高效地筛选新型候选膜材料。
英文摘要：
Anion exchange membranes are used in alkaline fuel cells and offer a promising alternative to the more expensive proton exchange membrane fuel cells. However, hydroxide ion conductivity in anion exchange membranes is low, and the quest for membranes with superior ion conductivity, mechanical robustness, and chemical stability is ongoing. In this study, we use classical molecular dynamics simulations to study hydroxide ion transport and mechanical properties of eight different hydrated polyolefin-based membranes, to provide a molecular-level understanding of the structure-function relationships in these systems. We examine the microstructure of the membranes and find that polymers with narrow cavity size distribution have tighter packing of water molecules around hydroxide ions. We estimate the self-diffusion coefficient of water and hydroxide ions and find that water molecules have a higher diffusion than hydroxide ions across all systems. The trends in hydroxide diffusion align well with experimental conductivity measurements. Water facilitates hydroxide diffusion, and this is clearly observed when the hydration level is varied for the same polymer chemistry. In systems with narrow cavities and tightly bound hydroxide ions, hydroxide diffusion is the lowest, underscoring the fact that water channels facilitate hydroxide transport. Finally, we apply uniaxial deformation to calculate the mechanical properties of these systems and find that polymers with higher hydration levels show poor mechanical properties. Atomistic molecular dynamics models can accurately capture the trade-off between hydroxide transport and mechanical performance in anion exchange membranes and allow us to screen new candidates more efficiently.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
