Rapid proton conduction through unfreezable and bound water in a wholly aromatic pore-filling electrolyte membrane.
Rapid proton conduction through unfreezable and bound water in a wholly aromatic pore-filling electrolyte membrane.
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DOI：
10.1021/jp810575u
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发表时间：
2009-03
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影响因子：
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通讯作者：
Nobuo Hara;H. Ohashi;Taichi Ito;Takeo Yamaguchi
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文献类型：
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作者：
Nobuo Hara;H. Ohashi;Taichi Ito;Takeo Yamaguchi
我们发现，尽管许多离子通常通过聚合物电解质中含有的自由水传导，但质子可以通过填充孔的电解质膜（PF膜）中的不可冻结的结合水快速传导。 PF-膜是一种独特的膜，由于其刚性聚酰亚胺基材，可以抑制填充磺化聚（亚芳基醚砜）（SPES）的膨胀。根据低温 DSC 测量，聚合物电解质的特殊结构导致强烈的溶胀抑制作用，仅产生不可冻结的结合水；它不含任何游离水。质子通过该结构快速传导。此外，随着填充的SPES的离子交换容量（IEC）的增加，质子传导的活化能从16.3 kJ/mol下降到9.1 kJ/mol，这与SPES铸膜的几乎恒定的值不同。 PF 膜的这种趋势是由于膜的结构而发生的，其中磺酸基团的浓度随着 IEC 的增加而增加，这通过利用填充 SPES 的膨胀抑制来挤压自由水成为可能。不受PF膜的限制，这种通过结构水和高浓度磺酸基团进行的独特质子传导将有助于开发未来的聚合物电解质，特别是在燃料电池领域，质子需要在各种条件下传导，例如低于0摄氏度的温度、高温和低湿度的组合以及燃料的存在。
We found that protons rapidly conduct through unfreezable and bound water in a pore-filling electrolyte membrane (PF-membrane), although many ions usually conduct through free water contained in polymer electrolytes. PF-membrane is a unique membrane that can suppress the swelling of filled sulfonated poly(arylene ether sulfone) (SPES) because of its rigid polyimide substrate. Based on low-temperature DSC measurements, this strong suppression of swelling resulting from the special structure of the polymer electrolyte results in unfreezable and bound water only; it does not contain any free water. Protons rapidly conduct through this structure. In addition, the activation energy of the proton conduction decreased from 16.3 to 9.1 kJ/mol in proportion to the increase in the ion exchange capacity (IEC) of the filled SPES, unlike the almost constant values of the SPES-cast membranes. This tendency of PF-membrane occurred because of the structure of the membrane, where the concentration of the sulfonic acid groups increased with increase in IEC, which became possible by squeezing free water using the swelling suppression of filled SPES. Without being constrained by the PF-membrane, this unique proton conduction through the structured water and highly concentrated sulfonic acid groups will help to develop future polymer electrolytes, particularly in the fuel cell field where protons need to conduct at various conditions such as temperatures below 0 degrees C, combined high temperature and low humidity, and the presence of fuels.