| 摘要: | 當今商業化的高溫型 PEMFC 所使用的薄膜材料為PBI(polybenzimidazole)，此高分子材料對磷酸具有良好的吸附能力，在高溫下能夠有良好的質子傳遞能力，但是高度的磷酸吸附能力卻弱化機械強度，另外此材料本身的價格昂貴不利於廣泛使用。因此開發一具有高質子傳遞能力、高化學穩定性以及具有足夠機械強度的質子交換薄膜是多年來研究相關材料學者的目標。
本研究所使用的高分子材料為具有高穩定性的磺酸化聚?。先前研究顯示此高分子對於磷酸有良好的吸附能力，操作溫度小於 160°C 時具有高度的質子傳遞能力。但當溫度大於 160°C 時，磷酸的滯留能力下降，質子傳遞能力也隨之下降。本研究藉由接枝氧化石墨烯(graphene oxide) 改善磺酸化聚?在高溫(大於 160°C)時薄膜的表現。該無機材料具有很好的熱、化學穩定性，其結構上又具有大量的含氧官能基(如:羥基、羧基、醚
基)，因此針對磷酸具有良好的吸附能力。然而氧化石墨烯在溶液中較不容易分散，本研究還進步將氧化石墨烯結構上增加了苯并咪唑(benzimidazole)官能基團；一方面是增加氧化石墨烯在溶液中的分散性，另外還可以增加對磷酸的吸附能力有利於提升質子傳遞。
在 PEMFC 的論文研究中，無機物添加的方法來改善薄膜的特性，其無機物的添加量都不超過 3%，主要原因是添加過多的無機物會導致薄膜機械強度過強，過於剛硬使其容易碎裂；另外過多的無機物會在薄膜中造成團聚分散性不佳，使薄膜的性能下降。為了能提高無機物在薄膜中的含量而不損失薄膜性能，本研究將無機物接枝於高分子的結構中，該方法可以避免無機物在薄膜中的聚集堆疊，改善薄膜的機械強度，不使薄膜過於剛硬或脆裂。在質子傳遞的測試中，於 25%磺酸官能化高分子中無機物
添加到 4 wt%時導電度明顯上升；而當磺酸官能化程度達 58%時，導電度卻可以持續上升直到無機物含量到 8 wt%。該結果說明提升官能基的程度可以增加無機物的添加量，進而達到有效提升導電度的目標。
另外，為了能進一步改善薄膜物性，本研究依據先前實驗室開發電場極化方法於薄膜的製作過程中施加電場。該場效極化效應使無機物以及高分子在薄膜中順向排列，使質子傳遞路徑能夠更短更筆直，進而提升傳遞效率。以 25%官能化高分子添加 4wt%官能基化氧化石墨烯，經過外加電場誘導之後導電度從原本的 1.28*10-2 S/cm 上升至 1.44*10-2 S/cm；而在 58%官能化 8 wt%氧化石墨烯接枝之高分子，經過外加電場誘導之後導電度從原本的 2.95*10-2 S/cm 上升至 3.4*10-2 S/cm。
最後在燃料電池的測試是選用 58%磺酸化磺酸化聚? 8wt%氧化石墨烯接枝之複合薄膜來進行測試，可以看到功率密度隨著溫度上升而上升，到 180°C 達最高點，開路電壓為 0.913V，功率密度達到 246.4 mW/cm2。此燃料電池功率密度接近商用 PBI 基礎的高溫質子膜之效果。;Benzimidazole Graphene functionalized Polysulfone(PSU) High temperature proton exchange membrane prepared under electric field poling Proton exchange membrane fuel cells (PEMFC) operating at high temperatures can have a
good tolerance for carbon monoxide poisoning catalysts, and operating at high temperatures can improve the overall operating efficiency of the battery, and it does not require a good management system for water…etc.
However, the key element that can demonstrate the high-temperature fuel cell is the proton exchange membrane. The membrane must have good proton transfer ability, and also need to have good thermal and chemical stability and mechanical strength to extend the fuel.
The thin film material used in the commercial high-temperature PEMFC is PBI (polybenzimidazole). This polymer material is selected because it has good adsorption
capacity for phosphoric acid and can have good proton transfer capacity at high temperature, but high adsorption capacity However, the mechanical strength is decreased. In addition, the high price of this material is not conducive to widespread use. Therefore, the development of
a proton exchange membrane with high proton transfer ability, high chemical stability and certain mechanical strength has been studied by related materials scholars for many years.
The polymer material used in this study is a sulfonated polymer with high stability. This polymer has good adsorption capacity for phosphoric acid and has a high proton transfer capacity when the operating temperature is less than 160°C. When the operating temperature
is greater than 160°C, the retention capacity of phosphoric acid decreases and the proton transfer capacity also decrease.
In order to improve the performance of the film at high temperatures (greater than 160°C), graphene oxide was also added in this experiment. This inorganic material has good thermal and chemical stability, and its structure has a lot of The oxygen-containing functional group
(such as: hydroxyl, carboxyl, ether), so it has good adsorption capacity for phosphoric acid.
However, graphene oxide is not easy to disperse in solution. In this study, graphene oxide was
additionally functionalized, and benzimidazole functional groups were added to the structure.
On the one hand, graphene oxide was added to the solution. In addition, it can increase the adsorption capacity of phosphoric acid to increase proton transfer.
In PEMFC’s thesis research, the method of adding inorganic substances to improve the characteristics of the film, the addition of inorganic substances is less than 2%, the main reason is that the addition of too much inorganic substances will lead to the mechanical
strength of the film is too strong, and the film is too rigid and easy to break. In addition, the dispersibility of inorganic substances in the film will also lead to the performance of the film.
Too much inorganic substances will cause agglomeration in the film and reduce the performance of the film.
In order to increase the content of inorganic substances in the film without losing the properties of the film, this study uses grafting to bond the inorganic substances in the polymer structure. This method can improve the mechanical strength of the film without causing The
film is too rigid and brittle; in addition, it also avoids the stacking of inorganic substances in the film. In the proton transfer test, it can be found that when the inorganic substance is added to 8%, the conductivity can always rise, indicating that this method can make the film
accommodate More inorganic substances will not reduce the performance of the film due to excessive inorganic substances.
In addition, in order to further improve the overall physical properties of the film, this study applied an electric field during the production process of the film based on the research methods of the previous laboratory, so that the inorganic substances and polymers can be
aligned in the film in order to enable the proton transfer path in the film. Shorter and straighter, thereby improving transmission efficiency.
The fuel cell test is the previous test result. It is tested with reference to the composite film added with 8wt% functionalized graphene oxide. It can be heated immediately and rises as the temperature rises, which is the highest at 180°C. The open circuit voltage is 0.913V, and the power density reaches 246.4 mW/cm2. |
