Comparison of Properties and Fuel Cell Performance of Nafion and Nafion/Silicon Oxide Composite Proton Conductive Membranes Derived from In-Situ Sol-Gel Process

利用In-Situ溶凝膠法所製備之Nafion／二氧化矽複合質子傳導膜的性質及其組裝於燃料電池的性能比較

林智汶(C. W. Lin) ； 曹金萍(C. P. Tsao)

《界面科學會誌》 27卷3&4期 (2005/09) Pp. 191-205

https://doi.org/10.30020/JCCIS.200509.0004

摘要

本文係以溶膠-凝膠法製備Nafion／silica（SiO2）複合膜並探討其應用於燃料電池質子交換膜之特性。動態機械性質分析顯示，複合膜的剛性隨著SiO2含量增加而增加。對未改質的Nafion而言，被指定為α鬆弛的玻璃轉移溫度（Tg）約為114.7℃，而β及γ鬆弛的溫度分別為12.0℃及-87.0，而複合膜的Tg及β鬆弛溫度均隨SiO2含量而增加，但屬於主鍊的局部鬆弛引起的γ轉移溫度溫度則並未受SiO2含量影響，此結果顯示SiO2只侷限在親水的離子團區域。原子力顯微鏡的研究顯示，薄膜表面的粗糙度高度受SiO2含量影響。當SiO2含在5.7%以下時，氧氣對薄膜的滲透率隨SiO2含量遞減，而含水率卻遞增。適當的SiO2含量下，雖然複合膜的質子傳導率並未明顯改變，但由於單位活性點的電流密度大幅增加，而以此複合膜作為質子交換膜所組單電池的性能得以改善。

關鍵字

Nafion／silica 複合膜 ； 溶膠-凝膠法 ； 燃料電池

並列摘要

Sol-gel derived Nafion/silica (SiO2) composite membranes were investigated with the viewpoint of fuel cell applications. Dynamic mechanical analysis showed an increase in stiffness of membrane with increasing SiO2 content. The glass transition temperature (Tg) assigned as α relaxation was measured 114.7℃ for the unmodified Nafion. An increase in Tg was found along the line of SiO2 content. Another two transition temperatures, assigned as β and γ relaxation were measured at 12.0℃ and -87.0℃, respectively. The β relaxation temperature increased with SiO2 content while γ transition arising from the local relaxation of main chain remains unchanged, which indicates that the incorporation of SiO2 was limited in the hydrophilic zone only. Surface imaging by tapping-mode atomic force microscopy (AFM) reveals the sharp increase in surface roughness at higher silica levels. Oxygen gas permeability of composites decreased with increase of SiO2 until 5.7% silica loading. Despite the higher water content, the proton conductivities of Nafion/SiO2 composites are lower than, or near to, that of unmodified Nafion membrane. In spite of slightly lower proton conductivities, composite membranes display better fuel cell performance. The current density of unit active surface area of composite with proper amount of silica is considerably higher than unmodified membrane.

並列關鍵字

sol-gel reactions ； Nafion/SiO2 composite ； fuel cells