Synthesis and Characterization of Sulfonated Polyether Ether Ketone (sPEEK) Electrolytes for PEM Fuel Cells: Effect of Sulfonation Degree

Abstract

This research is concerned with the synthesis and characterization of sulfonated polyether ether ketone (sPEEK) membranes which may be an alternative to commercial membranes used as proton carriers in proton exchange membrane (PEM) fuel cells. In this study, membranes of different degree of sulfonation were produced by sulfonation of pure PEEK membrane matrix at different times (1, 2 and 3 hours). Structural and thermomechanical characterization of prepared membranes were performed and proton conductivity was determined under standard fuel cell conditions. Thermomechanical behavior and proton conductivity of sulfonated polymeric membranes were evaluated according to the degree of sulfonation. The thermal strengths of the membranes were examined by thermogravimetric analysis (TGA) and all products showed high thermal stability for standard fuel cell operating conditions. Proton conductivity values and ion exchange capacities increased with sulfonation time and degree of sulfonation and highest conductivity values were observed in sPEEK-3 membranes prepared with a degree of sulfonation of 81.44%. The maximum proton conductivity (3.38x10-2 S/m) for sPEEK-3 membranes in the 300-330 K temperature range was reached at 330 K temperature. The mechanical strength of sPEEK-3 membranes was investigated by dynamic mechanical analysis (DMA) and storage module (E ’: 0.23 GPa) and glass transition temperature (Tg: 143oC) values were comparable to those of commercial Nafion 212 proton carrier membranes. As a result of this study, the thermomechanical stability and conductivity values of the prepared sPEEK-3 membranes were found to be an alternative level under standard PEM fuel cell operating conditions.

Keywords

• Fuel cell; PEM; conductivity; polyether ether ketone.

PEM Yakıt Hücreleri için Sülfone Polieter Eter Keton (sPEEK) Elektrolitlerin Sentezi ve Karakterizasyonu: Sülfonasyon Derecesi Etkisi

Abstract

Bu araştırma, proton değişim membran (PEM) yakıt hücrelerinde proton taşıyıcı olarak kullanılan ticari membranlara alternatif olabilecek sülfone polieter eter keton (sPEEK) membranların sentezi ve karakterizasyonu ile ilgilidir. Çalışmada saf PEEK membran matrisinin farklı sürelerde (1, 2 ve 3 saat) sülfonasyonuyla, sülfonasyon derecesi farklı membranlar üretilmiş, hazırlanan membranların yapısal ve termomekanik karakterizasyonu gerçekleştirilerek standart yakıt hücresi çalışma koşullarında proton iletkenlikleri belirlenmiştir. Hazırlanan sülfone polimerik membranların termomekanik davranışları ve proton iletkenlikleri sülfonasyon derecelerine bağlı olarak değerlendirilmiştir. Membranların termal dayanımları termogravimetrik analizlerle (TGA) incelenmiş, tüm ürünler standart yakıt hücresi çalışma koşulları için yüksek termal kararlılık sergilemişlerdir. Proton iletkenlik değerleri ve iyon değişim kapasiteleri sülfonasyon süresi ve sülfonasyon derecesiyle artmış, en yüksek iletkenlik değerleri % 81.44 sülfonasyon derecesi ile hazırlanan sPEEK-3 membranlarında gözlenmiştir. sPEEK-3 membranları için 300-330 K sıcaklık aralığında en yüksek proton iletkenlik değerine (3.38x10^-2 S/m) 330 K sıcaklıkta ulaşılmıştır. sPEEK-3 membranların mekanik mukavemeti dinamik mekanik analizle (DMA) incelenmiş, depolama modülü (E’: 0.23 GPa) ve camsı geçiş sıcaklığı (T_g: 143^oC) değerlerinin ticari Nafion 212 proton taşıyıcı membranlarla mukayese edilebilir seviyelerde olduğu gözlenmiştir. Bu çalışma sonucunda, hazırlanan  sPEEK-3 membranlarının termomekanik kararlılıklarının ve iletkenlik değerlerinin standart PEM yakıt hücresi işletme koşullarında alternatif olabilecek düzeyde olduğu görülmüştür.

Keywords

• Yakıt hücresi,PEM,iletkenlik,polieter eter keton

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