Clarification of Proton Conduction Processes in Radical-doped Perfluorosulfonic Acid Ion Exchange Membranes Using Elastic Recoil Detection Technique

通过直流电阻和交流阻抗测量，发现了室温下γ射线辐照约50 kGy的全氟磺酸膜的新的质子传导过程。在空气中300k时，膜的电导率比未辐照膜的电导率提高了约三个数量级。利用弹性反冲检测（ERD）技术，观察到辐照聚合物近表面的氢含量增加到未辐照聚合物的两倍。此外，通过水接触角测量发现，亲水性自由基的产生提高了材料的吸水性能。通过紫外、可见光和红外光学吸收以及氢离子交换容量测量，揭示了辐射诱导缺陷，如氟碳和过氧自由基，以及羰基中包含的C=O键与新的质子传导过程有关。由于近表面区域的辐射缺陷对氢吸收特性的改变导致质子电导率的增强。

New protonic conduction processes of perfluorosulfonic acid membranes by gamma-ray irradiation at a dose of up to approximately 50 kGy at room temperature in air have been found by direct current resistance and alternative current impedance measurements. The conductivities of the membranes at 300 K in air were enhanced to approximately three orders of magnitude higher than the conductivities of an unirradiated membrane. The hydrogen content in the near-surface region of the irradiated polymers was observed to increase to twice that of the unirradiated polymer by using the elastic recoil detection (ERD) technique. In addition, it was found by the water contact angle measurements that the water absorption characteristics were enhanced due to the production of hydrophilic radicals.By means of ultraviolet, visible, and infrared optical absorption and by hydrogen-ion-exchange capacity measurements, it was revealed that radiation-induced defects such as fluorocarbon and peroxy radicals, and C=O bonds included in carbonyl groups were related to the new proton conduction processes. The modification of hydrogen absorption characteristics due to the radiation-induced defects in near-surface regions leads to the enhancement of the proton conductivity.