水與甲醇在磺酸化聚電解質膜材之輸送現象探討

The transport of water and methanol in sulfonated polyelectrolyte membranes

李和謙(Ho-Chung)

指導教授 ： 孫一明

元智大學/工程學院/化學工程與材料科學學系/碩士(2004年)

摘要

本研究利用磺酸化聚電解質膜材－ sulfonated poly(phthalazinone ether ketone) (SPPEK) 以製備於燃料電池中的質子交換膜材，SPPEK 膜材以溶鑄法於玻璃板上成膜；所使用的鑑定方法包含動態機械分析儀、離子傳導率分析、元素分析、ATR-FTIR 官能基分析、水與甲醇的膨潤性測試、甲醇水溶液的滲透蒸發實驗、甲醇吸附實驗及水吸附實驗，其結果並與Nafion-117 的膜材性質作比較，以求驗證應用於直接甲醇燃料電池之膜電極組的可行性。
SPPEK膜材隨著磺酸化程度的增加，玻璃轉移溫度隨之下降；磺酸化程度的提升及溫度的上升，有助於離子傳導性的傳導；由滲透蒸發實驗，各類型SPPEK 膜材的通量[低於400 kg×μm/(h×m2)]都比Nafion-117 [約900 kg×μm/(h×m2)]低，且在滲透物的組成方面，各類型SPPEK 膜材中對甲醇的滲透量都比Nafion-117低，可避免在直接甲醇燃料電池上，甲醇滲透溢流 (crossover) 現象的產生。
在甲醇蒸氣吸附實驗中，低磺酸化程度的SPPEK膜材可以用Henrry’s law的吸附行為敘述，而SPPEK-121及Nafion-117以類似BET的吸附行為來描述。於30℃，甲醇及水蒸氣在SPPEK膜材內的擴散係數(D)約為 6.94×10-10 至 1.01×10-8 cm2s-1，比在Nafion-117膜材中為低(D = 2.0×10-8至 1.64×10-7 cm2s-1)。若使用SPPEK膜材，甲醇比較不易擴散到陰極端，應可利用於直接甲醇燃料電池上，提升燃料電池的性能。

關鍵字

質子交換膜、滲透現象、擴散係數、直接甲醇燃料電池

並列摘要

In this study, sulfonated poly(phthalazinone ether ketone) (SPPEK) membranes were prepared by the solvent casting method. The membranes could be used as the proton exchange membranes (PEM) in direct methanol fuel cell. A series of characterization studies were carried out to obtain the membrane properties, such as dynamic mechanical analysis, AC impedance analysis, element analysis, ATR-FTIR, water and methanol uptake measurement, pervaporation, and the measurement of the sorption and desorption kinetics of methanol or water vapors in the membrane. The properties of SPPEK membranes were compared with those obtained from Nafion-117.
The proton conductivity of the SPPEK membranes increased with temperature and their degree of sulfonation (DS). The glassy transition temperature of SPPEK decreased as the degree of sulfonation increased. SPPEK membranes may have lower fuel crossover than Nafion-117 membranes because SPPEK is a less permeable material than Nafion. The normalized permeation flux and permeated methanol in a pervaporation study showed lower values for SPPEK membranes than for Nafion-117 membranes.
The sorption isotherms of methanol in SPPEK could be explained by Henry’g law model when the DS of SPPEK was low. However, it became BET-type sorption when the DS of SPPEK was high and it was similar to that of Nafion. The diffusion coefficient of methanol in SPPEKs ranged from 6.94×10-10 to 1.01×10-8 cm2s-1, and it in Nafion ranged from 2.0×10-8 to 1.64×10-7 cm2s-1 at 30 oC. The use of SPPEK might be advantageous in reducing methanol crossover in a DMFC application.

並列關鍵字

proton exchange membrane, crossover, diffusion coefficient