TY - JOUR
T1 - Phase separation and ion conductivity in the bulk and at the surface of anion exchange membranes with different ion exchange capacities at different humidities
AU - Kimura, Taro
AU - Akiyama, Ryo
AU - Miyatake, Kenji
AU - Inukai, Junji
N1 - Funding Information:
This work was supported by the CREST program of the Japanese Science and Technology Agency (JST) . The authors thank Prof. Donald A. Tryk of the University of Yamanashi for his help in editing this manuscript.
Funding Information:
This work was supported by the CREST program of the Japanese Science and Technology Agency (JST). The authors thank Prof. Donald A. Tryk of the University of Yamanashi for his help in editing this manuscript.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2018/1/31
Y1 - 2018/1/31
N2 - 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−1obtained by small-angle X-ray scattering. At the temperature of 40 °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.
AB - 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−1obtained by small-angle X-ray scattering. At the temperature of 40 °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.
KW - Anion exchange membrane
KW - Atomic force microscopy
KW - Ion exchange capacity
KW - Small-angle X-ray scattering
KW - Transmission electron microscopy
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U2 - 10.1016/j.jpowsour.2017.06.081
DO - 10.1016/j.jpowsour.2017.06.081
M3 - Article
AN - SCOPUS:85023174336
SN - 0378-7753
VL - 375
SP - 397
EP - 403
JO - Journal of Power Sources
JF - Journal of Power Sources
ER -
