ePTFE之性質及其在燃料電池應用之研究

Properties of ePTFE membrane and its application on fuel cell

蔡政修(Cheng-Hsiu Tsai)

指導教授 ： 陳玉惠

中原大學/理學院/化學研究所/碩士(2007年)

https://doi.org/10.6840/cycu200700502

摘要

第一部份

本研究主要以Nafion溶液與ePTFE孔洞性基材製備一完整而連續填充之ePTFE/Nafion複合質子交換薄膜(ePN Composite Proton Exchange Membrane)。結果顯示複合膜的性能優劣應考量膜組成、保水能力等性質外，亦需注重複合膜中複合層填充情況之好壞。其中NP1複合膜導電度(Conductivity)為2.03×10-2S/cm，略低於Nafion115、Nafion117，但若考慮其膜厚因素，其Conductance為8.1S/cm2，比起Nafion115、Nafion117高出3.5、13.5倍。在保水能力方面，ePN系複合膜約24~27wt%，低於Nafion系膜之34wt%。導入ePTFE之孔洞基材後不僅可增加其複合膜機械強度，亦可抑制其在水合後之尺寸變化。PEMFC單電池在電池電壓為0.4V時之效能為：電流密度(Current Density)依序為Nafion-112(2574mA/cm2)≈ ePN-1(2573mA/cm2)＞ePN-2(1702mA/cm2)＞Nafion-115(1564mA/cm2)＞ePN-3(659mA/cm2)。功率密度(Peak of Power Density)則依序為ePN-1(1100mW/cm2)＞Nafion-112(1060mW/cm2)＞ePN-2(700mW/cm2)＞Nafion-115(650mW/cm2)＞ePN-3(260mW/cm2)。

第二部分

藉以不同波長之紫外光(Ultraviolet, UV)燈源對ePTFE膜進行照射，利用SEM、Static Contact Angle Analyzer、FTIR-ATR、ESCA、正子消散時間光譜儀探討其對ePTFE內部微結構之影響。由SEM可知在UVC長時間照射後，可明顯觀察ePTFE之纖維、節點被破壞。由接觸角結果可知其對水或對油之接觸角同時降低，這與ePTFE孔洞變化有關。另可由ATR圖譜觀察得知，在UV照射後之PTFE特徵峰因UV照射致使-C-F-斷鍵而明顯降低。
藉由此UV照射方法，適當調整其照射條件後(照射波長、照射時間、照射距離等)，可改變PTFE膜材之型態(Morphology)與物理性質，如孔洞大小(Pore size)、表面張力(Surface tension)、接觸角(Contact Angle)、拉伸強度(Tensile Strength)、屈服強度(Yield Point)、表面能(Surface energy)、表面結構(Surface Structure)，將其加以調控增加PTFE系膜材在高功能性材料上之應用範圍。

關鍵字

PTFE ； 燃料電池

並列摘要

第一部份

Porous expanded polytetrafluoroethylene (ePTFE) membranes were used as support material 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 PEMFC 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.

第二部分

Irradiation of pure PTFE membrane by Ultra Violet (UV) can change membrane morphology and some physical properties, such as pore size, surface tension, water contact angle, tensile strength, yield point, and surface structure, etc. The present research work investigated the properties of extended PTFE (ePTFE) membrane irradiated with different UV light sources.
The surface morphology of ePTFE membrane was studied using a scanning electron microscope (SEM). It was found that the fibers and nodes on the sample surface were destructed after UV irradiation. Contact angle and interfacial tension was investigated by static contact angle analyzer and found that water and/or oil contact angles of the irradiated membranes decreased with increasing irradiation time. This is ascribed to the increase of pore size of the membrane caused by the UV irradiation. The change of chemical bonding of the membrane was analyzed by the attenuated total-reflection FTIR spectroscopy (FTIR-ATR). It indicated that the intensity of the C-F vibration absorbance was reduced after UV irradiation, confirming the occurrence of the bond cleavage. The results suggest that the morphologies of ePTFE membrane can be controlled by adjusting the UV irradiation condition. Thus, this simple technique may extend ePTFE membrane to new applications.

並列關鍵字

PTFE ； fuel cell

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