TY - JOUR
T1 - Wet/dry cycle durability of polyphenylene ionomer membranes in PEFC
AU - Tanaka, Toshiki
AU - Shintani, Haruhiko
AU - Sugawara, Yasushi
AU - Masuda, Akihiro
AU - Sato, Nobuyuki
AU - Uchida, Makoto
AU - Miyatake, Kenji
N1 - Funding Information:
This work was partly supported by the New Energy and Industrial Technology Development Organization (NEDO) , by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Japan through Grant-in-Aids for Scientific Research (18H05515), by Japan Science and Technology (JST) through SICORP ( JPMJSC18H8 ), by JKA promotion funds from AUTORACE, and by thermal and electric energy technology foundation.
Funding Information:
Post-test analyses of the MEAs. After the durability test, both cells were disassembled and the recovered MEAs were subjected to the He leak test. Fig. 2 (b), (c) shows the amount of permeated He through the MEAs at 36 different locations. The MEA with the hard GDLs showed high He leakage (ca. 1.52 × 10−4 m3 Pa/sec on average). Significant He leak over the detection limit was observed at the edge of the catalyst layer (the boundary with the sub-gasket). Strain due to the swelling and shrinkage during the wet/dry cycle test occurred in the ionomer membrane, which caused mechanical failure, in particular, at the interface of the membrane and the catalyst layer under the gasket where the membrane was fixed and the dimensional change was restricted. The MEA with the soft GDLs exhibited much smaller He leakage (ca. 3.44 × 10−5 m3 Pa/sec on average). It is noted that the maximum He leakage was 6.56 × 10−5 m3 Pa/s, 69% smaller than that with the hard GDLs at the same location. During the wet/dry cycles, stress was concentrated on the edges of the membrane where significant dimensional changes occurred with the hard GDL. The soft GDL, which was adhered to the catalyst layer, deformed in accordance with the membrane swelling and shrinkage, and mechanically held it to prevent the membrane rupture (Fig. 3).The He leakage of the post-test SPP-QP membrane with the soft GDLs was even smaller than that of the post-test SPK membrane (ca. 1.0 × 10−4 m3 Pa/s on average) [18], further supporting the above-mentioned idea on the better durability of the SPP-QP membrane.Fig. 4 (c), (d) shows 1H NMR spectra of the post-test membranes at three different locations (similar to the GPC analyses) and the pristine membrane. In both membranes, the NMR spectra of the samples at the center and the edge were in fair agreement with that of the pristine membrane. Close examination revealed that peak 5, assignable to the sulfophenylene protons, was slightly smaller in intensity at the center and under the sub-gasket. The copolymer composition and IEC values were calculated from the peak integrals and are summarized in Table 3 to confirm that the changes in the composition and the concentration of the sulfonic acid groups were minor at all locations. The results further support the chemical robustness of the SPP-QP membrane in wet/dry cycle testing for 30,000 cycles.This work was partly supported by the New Energy and Industrial Technology Development Organization (NEDO), by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Japan through Grant-in-Aids for Scientific Research (18H05515), by Japan Science and Technology (JST) through SICORP (JPMJSC18H8), by JKA promotion funds from AUTORACE, and by thermal and electric energy technology foundation.
Publisher Copyright:
© 2021 The Authors
PY - 2021/8
Y1 - 2021/8
N2 - The mechanical durability of our hydrocarbon polymer electrolyte membrane, poly(sulfophenylene quinquephenylene) (SPP-QP) or polyphenylene ionomer, was evaluated in wet/dry cycle tests in fuel cells according to the US-DOE protocol, where the effect of gas diffusion layers (hard or soft GDL) was investigated. The membrane exhibited mechanical failure with the hard GDL and H2 crossover (permeation through the membrane) jumping from 0.01% to ca. 2% after 4,000 cycles. Post-test analyses indicated that the edge of the membrane under the gasket was the most damaged, where the dimensional change upon humidification/dehumidification was restricted. Use of the soft GDL significantly improved the wet/dry cycle durability of the membrane with no practical changes in the H2 crossover, even after 30,000 cycles, due to the strong adhesion of the GDL to the catalyst layers. The mechanical durability of the SPP-QP membrane was better than that of our previous aromatic-based ionomer membrane containing ether and ketone groups in the main chain. The loss of molecular weight and the sulfonic acid groups was rather minor for the SPP-QP membrane, indicating chemical robustness of the membrane under the severe wet/dry cycle conditions.
AB - The mechanical durability of our hydrocarbon polymer electrolyte membrane, poly(sulfophenylene quinquephenylene) (SPP-QP) or polyphenylene ionomer, was evaluated in wet/dry cycle tests in fuel cells according to the US-DOE protocol, where the effect of gas diffusion layers (hard or soft GDL) was investigated. The membrane exhibited mechanical failure with the hard GDL and H2 crossover (permeation through the membrane) jumping from 0.01% to ca. 2% after 4,000 cycles. Post-test analyses indicated that the edge of the membrane under the gasket was the most damaged, where the dimensional change upon humidification/dehumidification was restricted. Use of the soft GDL significantly improved the wet/dry cycle durability of the membrane with no practical changes in the H2 crossover, even after 30,000 cycles, due to the strong adhesion of the GDL to the catalyst layers. The mechanical durability of the SPP-QP membrane was better than that of our previous aromatic-based ionomer membrane containing ether and ketone groups in the main chain. The loss of molecular weight and the sulfonic acid groups was rather minor for the SPP-QP membrane, indicating chemical robustness of the membrane under the severe wet/dry cycle conditions.
KW - Fuel cells
KW - Mechanical durability
KW - Polyphenylene ionomers
KW - Proton exchange membranes
KW - Wet/dry cycles
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U2 - 10.1016/j.powera.2021.100063
DO - 10.1016/j.powera.2021.100063
M3 - Article
AN - SCOPUS:85109429416
SN - 2666-2485
VL - 10
JO - Journal of Power Sources Advances
JF - Journal of Power Sources Advances
M1 - 100063
ER -