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Cross-linker effect in ETFE-based radiation-grafted proton-conducting membranes, 2; Extended fuel cell operation and degradation analysis

ETFE基材の放射線グラフトプロトン伝導膜における架橋剤効果,2; 長時間の燃料電池作動と劣化解析

Ben youcef, H.*; Gubler, L.*; 八巻 徹也; 澤田 真一; Alkan G$"u$rsel, S.*; Wokaun, A.*; Scherer, G. G.*

Ben youcef, H.*; Gubler, L.*; Yamaki, Tetsuya; Sawada, Shinichi; Alkan G$"u$rsel, S.*; Wokaun, A.*; Scherer, G. G.*

本研究では、エチレン-テトラフルオロエチレン共重合体(ETFE)基材の放射線グラフトプロトン伝導膜における化学安定性に対し架橋剤量の効果を検討した。過酸化水素水溶液を用いた加速試験では、(1)架橋剤の導入により安定性が向上するが、過剰な導入は化学的,機械的特性が低下させること,(2)ETFE基材のプロトン伝導膜はテトラフルオロエチレン-ヘキサフルオロプロピレン共重合体(FEP)基材の場合よりも安定性に優れていること、の2点が明らかになった。グラフト率を25%に制御して作製したプロトン伝導膜を用い2180時間に渡るH$$_{2}$$/O$$_{2}$$燃料電池の作動試験を80$$^{circ}$$Cで行ったところ、水素透過量の増加に伴いセル電圧が平均で13$$mu$$V/h(電流密度500mA/cm$$^{2}$$)の速度で劣化した。作動運転後に、膜のモルフォロジー変化を解析した結果、O$$_{2}$$導入口付近などにおいて局所的に大きな劣化分解が確認された。

The effect of cross-linker content on the chemical stability of poly(ethylene-${it alt}$-tetrafluoroethylene) (ETFE)-based radiation-grafted and sulfonated membranes was investigated. An ex situ degradation test in hydrogen peroxide solution showed a strong increase in stability of crosslinked membranes compared to uncrosslinked ones. Excessive crosslinking, however, is detrimental to the chemical and mechanical properties. Furthermore, the stability of grafted membranes based on ETFE was superior to those based on poly(tetrafluoroethylene-${it co}$-hexafluoropropylene) (FEP). An in situ long-term test in a hydrogen/oxygen single cell over 2180 h, using an ETFE-based grafted membrane optimized with respect to cross-linker content, with a graft level of 25% was carried out. The performance of the membrane electrode assembly exhibited a voltage decay rate of 13 $$mu$$V/h over the testing time at a current density of 500 mA/cm$$^{2}$$ and a cell temperature of 80$$^{circ}$$C, while the hydrogen permeation showed a steady increase over time. This indicates that, to some extent, changes in the membrane morphology occur over the operating period. Local postmortem analysis of the tested membrane reveals that high degradation was observed in areas adjacent to the oxygen inlet and in other areas nearby.

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パーセンタイル:51

分野:Electrochemistry

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