Applications of Perfluorosulfonated Composite Membranes onProton Exchange Membrane Fuel Cell 1. Nafion/TiO2 composite membranes2. PTFE/Nafion composite membranes
| Autor: | Shih-Yang Chen, 陳世揚 |
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| Rok vydání: | 2007 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 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. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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