| Popis: |
Isopropanol fuel cells offer a promising way to provide electric energy from a liquid, non-toxic fuel. The secondary alcohol isopropanol is converted into acetone without producing significant amounts of CO2. The oxidation product acetone can be easily hydrogenated back to isopropanol to close the storage cycle, thereby avoiding fugitive molecular hydrogen with its low volumetric energy density at ambient conditions. Until now, electrodes and membranes for Direct Isopropanol Fuel Cells (DIFC) usually rely on various perfluorosulfonic acid derivates, like Nafion. Besides its high cost and unfavorable high fluorine content, the dissolution of Nafion in isopropanol mixtures has prevented the long time operation of DIFCs so far. Ionomer swelling during operation promotes efficiency-reducing crossover of isopropanol and acetone. This study introduces a new click-like covalent cross-linking strategy for fluoroaromatic ion-exchange polymers. Combined with ionic cross-linking of polymer blends, membranes with increased isopropanol stability were manufactured and compared to commercial Nafion membranes. The ionic and covalently cross-linked membrane resists a dissolution stress test up to 84 w-% and reduces the detected isopropanol/acetone crossover up to 75/100 % during fuel cell operation. Consequently, the cross-linking procedure and respective membrane material can be considered a significant step toward the technical implementation of DIFCs. |
