燃料電池質子交換膜仍有幾個缺點待改善，如(1)高溫失水，使質子導電度因缺乏傳遞介質而損失導電度、(2)燃料竄透，儘管有高的質子導電度也會因嚴重的燃料竄透而無法彰顯其效能、(3)耐久穩定性，薄膜須具有良好的機械與化學穩定性延長使用壽命。同時改進以上缺點是極大的挑戰，但目前仍無完整的方案。 本研究利用具有親水性質之PES添加至sPEEK高分子中，並於外加強電場下鑄造成質子交換膜。研究顯示，經由強電場誘導後sPEEK與PES高分子受到電場極化，薄膜中親水孔道在垂直於薄膜表面的方向形成具有方向性的優先取向結構，而此結構大幅的改善離子導電度。施加電場使更多的磺酸根基團顯露於親水域表面參與質子的運送，也使質子導電度大幅增加。此外，施用電場讓疏水區產生密緻化，降低了薄膜的膨潤率、燃料竄透性及提高其機械強度和化學穩定性。添加有機物PES至sPEEK中所製備的有機複合薄膜，在經電場誘導後，3PES/E之薄膜具有高達7.43×10-2 S/cm的質子導電度，在高溫低濕(80℃、20%RH)環境下仍可保持9.69x10-4 S/cm。製做成MEA之DMFC效能在80℃下可達到170 mW/cm2的輸出功率相較於市售薄膜N117的100 mW/cm2的效果更佳。 本研究指出磺酸化程度為基本條件，但提高質子導電度更有效的方法卻不是提高磺酸化程度，而是在膜材中構建具順向性排列的親水流通管道，更有效的利用磺酸根及便捷的傳輸路徑，如此可以使用較低的含水量以大幅提升質子傳導效率。此一新穎製備薄膜方法優化親水孔道的形貌紋理結構特徵，改善質子交換膜導電度，也同時改進了高溫失水、燃料竄透、耐久穩定性等多項物性，有效解決目前燃料電池膜材開發面臨的兩難窘況，該新穎膜材製備方法也能廣泛應用於各不同再生能源裝置所需膜材之開發。;There are few drawbacks in fuel cell proton exchange membranes that need implementation. They include: (1) dehydration of water at high-temperature leads to poor conductivity, (2) severe fuel permeability and cross-over suppresses power output; (3) weak membrane strength and insufficient chemical stability for long term operation. Improving upon all these deficiencies is a challenging task in fuel cell membrane development. Proton exchange membrane bears hydrophilic channel saturated with ion conducting medium, water. Ion transport is therefore heavily contingent upon the microstructure of this morphological texture. However, relationships between these structural features with ion conductivity have rarely been discussed. Even fewer are the studies of improvement on ion conductivity by means of tailoring channel morphology. Present research uses external electric field poling to create preferentially ordered channel morphology with high structural integral hydrophobic region in the membrane, has shown to effectively improved all prior-mentioned deficiencies. Validity of this approach is demonstrated in the miscible sPEEK/PES composite processed under electric field. The study has demonstrated that electric poling treatment created membrane bearing preferentially ordered hydrophilic channel morphology and densely packed hydrophobic region. Due to more densely packed amorphous hydrophobic domain, the membrane showed lower degree of swelling in water and methanol, and improved mechanical strength and chemical stability. The composite membrane of 3PES/E shows the proton conductivity up to 7.43x10-2 S/cm. Also at the high temperature and low humidity (80℃, 20%RH) environment can still maintain 9.69x10-4 S/cm. Nearly 60% increase of DMFC power output is observed using this membrane, and the best power density is recorded at 170 mA/cm2 (80℃, 1M Methanol). These results made it clear that although high degree of sulfonation is essential to ion conductivity, it is actually more efficient to elevate ion conductivity through architected hydrophilic channel morphology that makes full utilization of the sulfonate groups and established more direct ion transport path. This approach effectively propelled ion conduction using materials bearing lower degree of sulfonation and resolved the long standing dilemma of fuel cell membrane development. The technique is also beneficial to the development of next generation high performance membrane developments encounter in many renewable energy technologies.
