全氟磺酸複合質子交換膜應用於燃料電池之研究
     1. Nafion/二氧化鈦複合質子交換膜
     2. PTFE/Nafion複合質子交換膜

摘要 PartⅠ. Nafion/二氧化鈦複合質子交換膜應用於燃料電池之研究本研究成功製備出三種具孔洞結構之銳鈦礦型TiO2。分別為以室溫離子溶液[Bmim][PF6]為模版製備之中孔洞TPF6 (SSA=122 m2/g)，以[Bmim][BF4]為模版製備之中孔洞TBF4 (SSA＝82 m2/g），以及未使用離子溶液以傳統方式製備之微孔洞Tconventional (SSA＝89 m2/g）。並以此三種TiO2為添加物與Nafion混摻後製成Nafion/TiO2複合質子交換膜，探討此複合膜在各種操作條件下之各項性能。從X射線繞射儀、比表面積/孔隙度及化學吸附分析儀、穿透式電子顯微鏡的綜合鑑定結果得知：TBF4及TPF6皆為中孔洞TiO2，且孔洞尺寸分佈狹窄，大小均一，其中TPF6除具最高之比表面積外，更具有最大量之中孔洞、最小孔洞尺寸及最佳熱穩定性。而Tconventional則是在450 ◦C的燒結過程中孔洞崩塌轉趨為微孔結構，且孔洞尺寸分佈較為寬廣。在單電池效能方面，當電池操作溫度為80 ◦C及90 ◦C時，所添加TiO2的比表面積大小為影響複合膜保水能力的主要因素。然而，當電池操作環境之相對濕度從95%降至50%，且電池操作溫度升高至110 ◦C或120 ◦C時，TiO2結構的孔洞尺寸及數量就變得相當重要，此兩因素將影響複合膜的失水速率，進而影響電池效能。本研究製備之Nafion/3wt.%TPF6複合膜在高操作溫度(120 ◦C)及低環境相對濕度(50% RH)下運作時，當操作電壓0.4V時的功率密度為重鑄Nafion膜的5.7倍。 Part Ⅱ. PTFE/Nafion複合質子交換膜應用於燃料電池之研究本研究利用較低成本且具高功能性之孔洞性ePTFE薄膜為基材，成功與全氟磺酸化離子型溶液複合成ePTFE/Nafion (ePN)複合質子交換膜。由SEM、AFM、UV-Vis、及氣體滲透儀的綜合鑑定結果得知：ePN系列複合膜之表面為均勻無細孔缺陷，而其中更以ePN-1複合膜，不論觀察表面或斷面，皆顯示Nafion樹脂連續而均勻地填充進入基材孔洞中。 ePN系列複合膜(ePN-1、ePN-2、ePN-3)之導電度隨Nafion填充量的增加而增大，導電度值由8.76×10-3 S/cm升高至2.03×10-2 S/cm。其中以ePN-1複合膜填充最為完全，故導電度最高。與純Nafion比較，導電度大小順序為：Nafion® 112＞ePN-1＞ePN-2＞Nafion® 117＞ePN-3。 ePN系列複合膜的含水能力略低於Nafion®系列膜，但機械性質與水合尺寸安定性方面卻優於Nafion®系列膜，且愈薄之ePN複合膜(ePN-1)具有愈好的機械性質與水合尺寸安定性。此ePN系列複合膜組裝成PEMFC單電池，在電池電壓為0.4V時之電流密度依序為： Nafion® 112 (2574 mA/cm2)≒ePN-1 (2573 mA/cm2)＞ePN-2 (1702 mA/cm2)＞Nafion® 115 (1564 mA/cm2)＞ePN-3 (659 mA/cm2)。

關鍵字

質子交換膜；離子溶液；燃料電池；二氧化鈦

並列摘要

Abstract PartⅠ. Nafion/TiO2 composite membranes for fuel cell applications Three high-purity TiO2 (anatase) powders (TPF6, TBF4, and Tconventional) were prepared by the sol-gel method with/without ionic liquid as template and calcinations at 450 ◦C. These powders were, then, characterized to investigate their differences in morphological properties. Electrochemical performances of the H2/O2 PEMFCs employing the Nafion composite membranes with these three TiO2 powders as fillers were studied over 80-120 ◦C under 50% and 95% relative humidity (RH). The result showed that the order of the fillers effect on the performance at 80 and 90 ◦C was the same as that of the TiO2 filler’s specific surface area (i.e. TPF6＞ Tconventional＞ TBF4＞ P25, a commercially available nonporous TiO2 powder). However, the order between Tconventional and TBF4 was reversed at 110 and 120 ◦C under 50% RH. This indicates that the size and the amount of mesopores, which better confined the water molecules, were significant contributing factors to the performances at the higher temperatures. The best power density obtained under 50% RH at 120 ◦C and a voltage of 0.4 V was from the PEMFC with the TPF6-containing Nafion composite membrane. It was about 5.7 times higher than the value obtained from that with the recast Nafion membrane. Part Ⅱ. PTFE/Nafion composite membranes for fuel cell applications Porous expanded polytetrafluoroethylene (ePTFE) membranes were used as support materials for ePTFE/Nafion composite membranes. The composite membranes were prepared by impregnating porous ePTFE membranes with a self-made perfluorosulfonated ionomer (PFSI) solution. Three ePTFE/Nafion composite membranes with different thickness were prepared in this study. The results of scanning electron micrographs (SEM) and oxygen permeabilities showed that the Nafion resin was distributed uniformly in the composite membranes and plugged the micropores. Besides, a continuous thin Nafion film was observed on the surface of each composite membrane. The resulting composite membranes were mechanically durable and quite thin relative to the commercial Nafion® membranes. In dry conditions, tensile strength of the ePTFE/Nafion composite membranes were larger than that of Nafion® 112 due to the reinforcing effect of the porous ePTFE films. The performances of the PEMFC with the as-prepared ePTFE/Nafion composite membranes were also tested on an in-house system. The results showed that the thinner of the composite membrane the better the cell performance. The best fuel cell performance was obtained from the PEMFC with the thin ePN-1 composite membrane, which was similar to that with Nafion® 112, but higher than that with Nafion® 115.

並列關鍵字

TiO2 ； ionic liquid ； fuel cell ； proton exchange membrane

參考文獻

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國際替代計量

全氟磺酸複合質子交換膜應用於燃料電池之研究 1. Nafion/二氧化鈦複合質子交換膜 2. PTFE/Nafion複合質子交換膜

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