Anomalous, Multistage Liquid Water Diffusion and lonomer Swelling Kinetics in Nafion and Nafion Nanocomposites
Anomalous, Multistage Liquid Water Diffusion and lonomer Swelling Kinetics in Nafion and Nafion Nanocomposites
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DOI：
10.1021/acsapm.9b00866
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发表时间：
2020-01-01
影响因子：
5
通讯作者：
Davis, Eric M.
中科院分区：
文献类型：
--
作者：
Balwani, Apoorv;Davis, Eric M.
商业上可行的钒氧化还原液流电池的出现引起了人们对改进这种电网规模能量存储技术中使用的现有膜材料的兴趣。阐明全氟磺化离聚物纳米复合材料中的结构-传输关系对于下一代膜的开发特别重要，因为对纳米颗粒如何改变这些膜中的传输的理解有限。在本研究中，我们试图解决的影响，二氧化硅纳米粒子（SiNPs）的液体水在Nafion-SiNP膜传输。具体而言，液体水的吸附和离聚物溶胀动力学在一系列的Nafion-SiNP膜进行了评价，使用时间分辨衰减全反射傅里叶变换红外光谱。在所有SiNP加载量下，观察到Nafion和Nafion-SiNP膜的异常多级吸水和溶胀动力学。第一阶段的动力学数据回归到扩散-松弛模型，因为发现在该第一阶段期间水扩散和所得的扩散诱导的聚合物松弛动力学是高度耦合的。随着SiNP的引入，观察到抑制的水传输和溶胀动力学，尽管这种趋势对于更高的SiNP负载并不成立。还观察到膜的热退火影响Nafion和Nafion-SiNP膜的传输和溶胀性质，在低纳米颗粒负载下表现出与SiNP的协同效应。最后，在干燥的Nafion和Nafion-SiNP纳米复合材料的多级吸水机制被理解为取决于时间的膜中的局部水活性。总的来说，这项研究提出了一个明确的框架，可以用来表征和调整通过Nafion纳米复合膜的水传输。
The advent of commercially viable vanadium redox flow batteries has generated interest in improving upon existing membrane materials utilized in this grid-scale energy storage technology. Elucidating structure-transport relationships in perfluorosulfonated ionomer nanocomposites is of particular importance for the development of next-generation membranes, as there is a limited understanding of how nanoparticles alter transport in these membranes. In the present study, we attempt to resolve the impact of silica nanoparticles (SiNPs) on liquid water transport in Nafion-SiNP membranes. Specifically, liquid water sorption and ionomer swelling kinetics in a series of Nafion-SiNP membranes were evaluated using time-resolved attenuated total reflectance-Fourier transform infrared spectroscopy. Anomalous, multistage water uptake and swelling kinetics were observed for both Nafion and Nafion-SiNP membranes at all SiNP loadings. The first stage of the kinetic data was regressed to a diffusion-relaxation model, as water diffusion and resulting diffusion-induced polymer relaxation kinetics during this first stage were found to be highly coupled. Suppressed water transport and swelling kinetics were observed with the introduction of SiNPs, though this trend did not hold true for higher SiNP loadings. Thermal annealing of the membranes was also observed to impact the transport and swelling properties of the Nafion and Nafion-SiNP membranes, exhibiting a synergistic effect with the SiNPs at low nanoparticle loadings. Finally, the multistage water uptake mechanism in dry Nafion and Nafion-SiNP nanocomposites was understood to be governed by the time-dependent local water activity in the membrane. Overall, this study presents a clear framework that can be employed to characterize and tune aqueous transport through Nafion nanocomposite membranes.