磷酸燃料電池 (Phosphoric acid fuel cell, PAFC) 為高溫型之燃料電池，其操作溫度為100-250oC，和質子交換膜燃料電池(Proton exchange membrane fuel cell, PEMFC) 比起來具備較高的一氧化碳毒化 (CO poisoning) 容忍度、可簡化水熱管理等好處。然而磷酸燃料電池卻有電解質隨著時間而洩漏的問題，影響到電池之長效穩定性，使其發展受到限制。
本研究以鹼性雙氧水改質之二氧化鈦 (Alkaline hydrogen peroxide modified TiO2, AHP-TiO2) 顆粒改質聚苯並咪唑薄膜 (Polybenzimidazole, PBI)，旨在提高薄膜留存水及磷酸之能力，以維持電池之長效穩定性。
為了觀察二氧化鈦改質前後的變化，本研究以FTIR確認鹼性雙氧水是否能提高二氧化鈦表面的OH官能基；由BET分析二氧化鈦之比表面積及孔徑分布，並搭配TGA之數據精確計算出表面氫氧官能基的密度。於PBI膜材方面，藉由SEM觀察膜材之表面形貌與厚度，並且以拉伸機測試其機械強度變化。
在電性表現方面，本實驗以交流阻抗法 (AC impedance analysis) 得知PBI膜之質子傳導度 (Proton conductivity)；並以燃料電池測試機台 (Mini 150) 測試本研究製備的質子交換膜應用於磷酸燃料電池之效能。經過眾多分析及測試後發現，添加2% AHP-TiO2的PBI膜可以提高約2倍的質子傳導度；電池測試方面，其最大功率密度在170oC時可達961mW/cm2；在長效測試方面，經過92 h的長效測試 (0.2A/cm2, 170oC) 後電池電壓僅下降3%。

Recently, high temperature fuel cells, such as phosphoric acid fuel (PAFC), have been studied. It has been previously reported that increasing the operation temperature of fuel cells can be advantageous to not only increase its electrocatalytic activities and tolerance to impurities (such as carbon monoxide), but also simplify the hydrothermal management system and increase overall energy conversion efficiency. However, the electrolyte in the membrane will leach out during operation, and this problem limits the development of phosphoric acid fuel cell.
In this thesis, in order to overcome the electrolyte leaching issue, we used polybenzimidazole (PBI) membrane as the substrate and developed the composite proton exchange membrane which was composed of the filler “titanium dioxide (TiO2)”. And then, we used alkaline hydrogen peroxide (AHP) to increase the hydroxyl group on the TiO2 surface to further enhance the durability of fuel cell.
About the characterization analysis, we used Fourier transform infrared spectroscopy (FTIR), BET and thermogravimetric analysis (TGA) to determine the enhancement of hydroxyl group on the TiO2 surface after AHP modification. Then we used scanning electron microscope (SEM) to observe the surface morphology and thickness of the PBI membrane. Tensile test was used to understand the effect of the addition of TiO2 on mechanical properties. Finally, we conducted AC impedance analysis to measure the proton conductivity and single cell test/life time test to know the performance of fuel cell.
The results show that the proton conductivity of 2% AHP-TiO2/RPBI was twice pristine PBI. In single cell test, the best performance of 2% AHP-TiO2/RPBI can reach 961 mW/cm2. In life time test, 2% AHP-TiO2/RPBI just decayed 3% of its voltage after 92 h of operation under 170oC and 0.2 A/cm2.

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