複合型質子傳導膜與其膜電極組於燃料電池的運用

Abstract

Abstract (in Chinese) 本論文中以改質的碳材去解決燃料電池目前所面臨的困境，研究內容分為三大主軸: 1. 改質的活性碳於氫氣燃料電池上的運用 藉由聚乙稀醇改質的活性碳作製備出來的質子交換膜具備高的飽水率，此複合質子交換膜利用乙烯醇作為質子的傳導媒介可以增加質子導電度與尺寸安定性，而這些都是燃量電池不可或缺的重要特性。除此，其機械性質也隨著無機物的添加而有顯著的進步性，使其在結構穩定適合不同溫度下的操作；而實際運用在氫氣電池，此複模膜的特性也比商用品要好上許多，在電池的測試過程中，我們利用其阻抗的變化去了解實際電池內部的變化。 2. 低甲醇穿透率的磺酸化氧化石墨烯/Nafion複合質子交換膜 低甲醇的質子交換膜可以藉由簡單且有效率的分散磺酸化氧化石墨烯於Nafion製備而成，藉由黏度的變化去判別其分散的情況；成膜後，此複合膜具備低的甲醇穿透度、好的尺寸安定性與在低濕環性下較好的質子導電度適用於甲醇燃料電池。 3. 新穎的雙層膜於被動式醇甲醇燃料電池上的運用 此雙層的複合質子交換膜是藉由重複塗佈磺酸化氧化石墨烯/Nafion與磺酸化活性碳/Nafion所製備而成，藉由控制溶劑與乾燥條件可以製備出厚度相似且均勻性佳的雙層膜，此雙層膜一端擁有低甲醇穿透度，另一端具備良好的飽水率，且此複合膜的質子到導電度高，適合運用在被動式純甲醇燃料電池，實際的電池效能顯示此複膜膜的放電特性優於商品Nafion 115與Nafion 117，有商業化的潛能。

.

Abstract (in English) In this study, we focus on the modification of materials and their application on fuel cells. 1. Poly(ethylene glycol) modified activated carbon for high performance proton exchange membrane fuel cells

A high water retention membrane is developed by co-assembling poly(ethylene glycol) (PEG) grafted activated carbon (AC-PEG) with Nafion. The AC-PEG is prepared via a sol-gel process. The use of PEG as a transporting medium in AC-PEG shows a largely improved water retention ability, a higher proton conductivity and a reduced swelling ratio, making it well suited for proton exchange membrane fuel cells (PEMFCs). Further, the composite membranes show improved mechanical properties at high temperature, thus ensuring the structural stability of membranes during the fuel cell operation. Compositional optimized AC-PEG/Nafion composite membrane (15 wt% compared to Nafion) demonstrates a better performance than the commercially available counterpart, Nafion 212, in fuel cell measurements. To identify the key factor of the improved performance, current interrupt technique is used to quantitatively verify the changes of resistance under different relative humidity environment.

2. Sulfonated graphene oxide/Nafion composite membranes with low methanol permeability

An easy and effective method for producing low methanol-crossover membranes is developed by dispersing sulfonated graphene oxide (SGO) into a Nafion matrix. A SGO/Nafion mixture with low SGO content exhibits unique viscosity behaviour and allows for better SGO dispersion within the Nafion. After film casting, the composite membranes show lower methanol and water uptakes, a reduced swelling ratio, improved proton conductivity in low relative humidity, and extremely high methanol selectivity, which can be implemented in direct methanol fuel cells (DMFCs).

3. Novel Bilayer Composite Membrane for Passive Direct Methanol Fuel Cells with Pure Methanol

The bilayer composite membrane composed of the sulfonated graphene oxide (SGO)/Nafion and sulfonated activated carbon (SAC)/Nafion composite membrane is designed and prepared by repeatedly bar-coating. With the carefully chosen of solvent, the bilayer composite membrane has shown identical thickness on SEM observation. The SGO/Nafion side has a low methanol permeability ascribed to the unique selectivity of the SGO. Moreover, the SAC side has good water retention which can facilitate the back diffusion water produced by the cathode. The unique design of composite membranes confers low methanol crossover and high proton conductivity at the same time. The bilayer composite membrane shows better power density than Nafion 212 and Nafion 115 and the performance monitored for 24h to ensure the stable power density and the durability of the membrane.