第一部份，我們說明了在質子交換膜燃料電池中使用金屬發泡材取代流場的實驗結果。這些實驗結果表明，質子交換膜燃料電池使用金屬發泡材為流場的重要特點，是比一般石墨板燃料電池更能提升電池的性能。實驗中比較了不同性質的金屬發泡材與石墨板燃料電池間的極化曲線。文中將說明質子交換膜燃料電池用金屬發泡材為流道所具有的特點。由於金屬發泡材的高孔隙率（可達80 ％以上），質傳限制的現象並不像在傳統的質子交換膜燃料電池上明顯。另一個有趣的現象是，發泡材金屬的導電性能扮演著重要的角色，這個現象很少出現在傳統的質子交換膜燃料電池。雖然有一些技術上的挑戰，例如；取代金屬發泡材流道板。但金屬發泡材其獨特的質傳現象，加上其重量輕，使得金屬發泡材在燃料電池上的應用具有非常大的吸引力。第二部份，我們報告如何藉由流場設計促進使用金屬發泡材為流道之質子交換膜燃料電池的性能。這些研究結果可以讓我們能更深入了解金屬發泡材的流場分布對於電池性能的影響。我們使用各種不同的金屬發泡材流場並將其極化曲線與傳統石墨雙極板燃料電池之極化曲線比較。實驗結果顯示，使用改良之金屬發泡材流場可提升燃料電池之性能。數種金屬發泡材流場設計與其特點在本文內有詳細的分析。因為氣體流動會受入口設計與發泡材的幾何外型所限制，不同的流場設計會影響到流動模式。我們的研究指出使用單區的金屬發泡材燃料電池，對流效果在角落會較低。將金屬發泡材劃分為多區域與使用多個入口後，能夠有效地增加氣體之分散與傳輸。本研究同時也利用交流阻抗儀測量金屬發泡材燃料電池的阻抗特徵。由奈奎斯特圖與波德圖可證實金屬發泡材燃料電池的各項阻抗 (歐姆阻抗、活化阻抗與質傳阻抗) 皆小於傳統的石墨雙極板燃料電池者。First, the experimental results of the PEM fuel cell with metal foam as flow distributor will be reported. These experimental results show the characteristics of the PEM fuel cell with the metal foam as flow distributor and extend our understanding of the relation between cell performance and mass transport properties into a region of parameters that the conventional PEM unit cell can not provide. The comparison in polarization curve is made between the PEM unit cell with different metal-foam properties and the PEM unit cell with graphite flow channel plate as flow distributor. The experimental results show that the PEM fuel cell with metal foam as flow distributor possesses some unique characteristics compared with the conventional PEM unit cell with flow channel plate as flow distributor. Due to the high porosity of metal-foam (over 80 %) plus convective flow through the metal-foam, mass transport limitation phenomenon is not as pronounced as in the case of conventional PEM unit cell with flow channel plate as flow distributor. Another interesting phenomenon is that electrical conductivity of metal-foam plays a significant role in performance, which is seldom the case in the conventional PEM unit cell with flow channel plate as flow distributor. Although there are several technical challenges to be overcome for the current form of metal-foam to replace flow channel plates, the unique mass-transport properties of metal foam plus its light weight are very attractive.In the second part, the improvements made on the PEM fuel cell with metal foam as the flow distributor are reported. The comparison in polarization curve is made between the PEM unit cell with different metal foam flow field designs and the PEM unit cell with graphite bipolar plate as flow distributor. The experimental results show that after using improved metal foam flow field designs, the fuel cell’s performance increases. Because the gas flow is limited by the flow inlet and the metal foam geometry, different flow field design will affect the flow pattern. the results show that, in the PEM unit cell with single zone metal foam, convection is weak at side corners. Dividing the metal foam into multiple regions and using multiple inlets effectively increases the gas distribution. AC impedance measurement was also performed to study the impedance characteristics. The Nyquist and Bode plots confirmed that Ohmic resistance, activation resistance, and mass transfer resistance of metal foam fuel cell are all smaller than that of conventional PEM unit cell.
