Phase separation and ion conductivity in the bulk and at the surface of anion exchange membranes with different ion exchange capacities at different humidities

JOURNAL OF POWER SOURCES

卷:375

Article

Kimura, Taro¹  Akiyama, Ryo²  Miyatake, Kenji^2,3  Inukai, Junji^2,3 

[1] Univ Yamanashi, Interdisciplinary Grad Sch Med & Engn, 4 Takeda, Kofu, Yamanashi 4008510, Japan

[2] Univ Yamanashi, Fuel Cell Nanomat Ctr, 6-43 Miyamae Cho, Kofu, Yamanashi 4000021, Japan

[3] Univ Yamanashi, Clean Energy Res Ctr, 4 Takeda, Kofu, Yamanashi 4008510, Japan

关键词: Anion exchange membrane;    Ion exchange capacity;    Transmission electron microscopy;    Small-angle X-ray scattering;    Atomic force microscopy;   

DOI  :  10.1016/j.jpowsour.2017.06.081

来源: Elsevier

【 摘 要 】

For higher performances of anion exchange membrane (AEM) fuel cells, understanding the phase separated structures inside AEMs is essential, as well as those at the catalyst layer/membrane interfaces. The AEMs based on quaternized aromatic semi-block copolymers with different ion exchange capacities (IECs) were systematically investigated. With IECs of 1.23 and 1.95 mequiv g(-1), the water uptakes at room temperature were 37% and 98%, and the anion conductivities 23.6 and 71.4 mS cm(-1), respectively. The increases were not proportional to the IEC. Images obtained by transmission electron microscopy in vacuum were similar with both IEC values, but the development of a clear phase separation in humidified nitrogen was observed in the profiles only with 1.95 mequiv g(-1) obtained by small angle X-ray scattering. At the temperature of 40 degrees C and the relative humidity (RH) of 30%, the average currents observed at the tip apex by current-sensing atomic force microscopy were <0.5 and 10 pA with 1.23 and 1.95 mequiv g(-1), respectively, and those at 70% RH were 10 and 15 pA, respectively. The humidity gave a larger influence on the bulk structure with 1.95 mequiv g(-1), whereas a larger influence on the surface conductivity with 1.23 mequiv g-1. (C) 2017 Elsevier B.V. All rights reserved.

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