Acid-functionalized polysilsesquioxane-nafion composite membranes with high proton conductivity and enhanced selectivity.
Acid-functionalized polysilsesquioxane-nafion composite membranes with high proton conductivity and enhanced selectivity.
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DOI：
10.1021/am900498u
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发表时间：
2009-10
影响因子：
9.5
通讯作者：
Kui Xu;Chalatorn Chanthad;M. R. Gadinski;M. Hickner;Qing Wang
中科院分区：
文献类型：
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作者：
Kui Xu;Chalatorn Chanthad;M. R. Gadinski;M. Hickner;Qing Wang
以3-（三羟基硅基）丙烷-1-磺酸为原料，采用原位溶胶-凝胶法和溶液浇铸法制备了一系列新型的Nafion基复合膜。的形态结构，离子交换容量，吸水率，质子传导率，和甲醇渗透性的复合膜已被广泛研究作为功能的磺丙基化聚倍半硅氧烷填料的含量，温度和相对湿度。与传统的全氟磺酸/二氧化硅复合材料，所制备的膜表现出增加的水吸收和相关的增强质子传导性相比，未改性的全氟磺酸。特别是，在80和120摄氏度和30%相对湿度下相当高的质子传导率已经在复合膜中得到证实，其比Nafion的高2倍以上。除了质子传导率的显著改善之外，与纯Nafion膜相比，复合膜显示出较低的甲醇渗透性和上级电化学选择性。这些独特的性能可以完全归功于在填料中存在的磺酸侧基，这在复合膜中的填料和基质之间提供了相当连续的质子传导路径，从而促进质子传输，而没有预期的电导率和选择性之间的权衡。这项工作开辟了新的机会，定制的性能的Nafion的基准燃料电池膜，克服其局限性，提高在高温/低湿度和直接甲醇燃料电池的导电性能。
A series of new Nafion-based composite membranes have been prepared via an in situ sol-gel reaction of 3-(trihydroxylsilyl)propane-1-sulfonic acid and solution casting method. The morphological structure, ion-exchange capacity, water uptake, proton conductivity, and methanol permeability of the resulting composite membranes have been extensively investigated as functions of the content of sulfopropylated polysilsesquioxane filler, temperature, and relative humidity. Unlike the conventional Nafion/silica composites, the prepared membranes exhibit an increased water uptake and associated enhancement in proton conductivity compared to unmodified Nafion. In particular, considerably high proton conductivities at 80 and 120 degrees C under 30% relative humidity have been demonstrated in the composite membranes, which are over 2 times greater than that of Nafion. In addition to a remarkable improvement in proton conductivity, the composite membranes display lower methanol permeability and superior electrochemical selectivities in comparison to the pure Nafion membrane. These unique properties could be exclusively credited to the presence of pendant sulfonic acid groups in the filler, which provides fairly continuous proton-conducting pathways between filler and matrix in the composite membranes and thus facilitates the proton transport without the anticipated trade-off between conductivity and selectivity. This work opens new opportunities of tailoring the properties of Nafion-the benchmark fuel cell membrane-to obviate its limitations and enhance the conductive properties at high temperature/low humidity and in direct methanol fuel cells.