- 學位論文
質子交換膜燃料電池陰極製造參數與單電池性能之研究
Study on the cathode fabrication parameters and single cell performance of Proton Exchange Membrane Fuel Cell
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摘要
本研究可分為兩個部分，其最終目的都是希望能提升質子交換膜燃料電池的性能。第一部分著重於質子交換膜燃料電池中陰極製造參數的最適化，實驗將從陰極觸媒層中不同Nafion與PTFE的添加比例、不同重量比的Pt/C觸媒、不同壓膜壓力以及不同厚度的薄膜來探討陰極最佳的製造參數。實驗將固定觸媒層中白金使用量為0.4mg/cm2，系統在無背壓情況下操作，操作溫度為60℃，在做I-V與EIS測試時需提供氧氣，其流量為65c.c./min、CV測試時需提供氮氣，其流量為100c.c./min，並以1M硫酸水溶液提供所需氫離子，而測試之陰極為使用轉印法所製成。測試結果顯示出使用10wt%Pt/C與20wt%Pt/C製成的陰極，其最佳性能出現在觸媒層中含有5wt%PTFE 和Pt/C:Nafion=1:0.1時，兩者皆能達到1.5A/cm2以上；而隨著PTFE比例的增加，10wt%Pt/C製成的電極性能會逐漸衰退，但是20wt%Pt/C製成的電極性能卻能保持一定；而使用100kg/cm2的壓力來壓膜可以得到電極最佳性能；Nafion 117因為其抵抗硫酸水溶液直接穿透的能力最強，因此在性能表現上也最優異。 本研究第二部分是從質子交換膜燃料電池單電池的外部參數來著手，包括電池溫度、陰陽極增濕溫度、陰陽極進料流量和進料成分，此部分的研究將使用塗佈法來製造膜電極組，陽極與陰極的白金觸媒用量皆為0.4mg/cm2，採用Nafion 117薄膜作為電解質，氣體擴散層為經過20wt%疏水處理的碳紙，觸媒層中Pt/C:Nafion=1:0.5，而測試用的單電池流道設計為2.4cm x 2.4cm的蛇形流道，有效反應面積約為5.76cm2。由實驗結果發現在固定的陰陽極進料參數下，隨著電池溫度的上升會使質子交換膜脫水而造成電池阻抗增加、電池性能下降；要得到電池最佳性能，陰陽極的進料增濕溫度需隨著電池溫度升降而做改變，在陽極進料為純氫、陰極進料為純氧下，電池溫度為45℃、陰陽極進料增濕溫度分別為45℃與35℃時，電池有最佳性能；而在電池溫度為65℃、陰陽極進料溫度分別為75℃與55℃時，電池有最佳性能；在陰陽極進料方面，本實驗皆固定陽極進料為純氫、流量為300c.c./min，由改變陰極進料流量與成分來觀察其對電池性能的影響，結果顯示出電池性能會隨著陰極進料流量的增加而上升，但流量超過300c.c./min時，性能就未有顯著的上升；而利用空氣取代純氧也使得電池性能大幅下降且在低電位時電流會不穩定跳動，係因空氣中的氧氣含量不足造成氧氣輸送困難，無法持續供給電化學反應所需之氧氣量。在陽極使用含有不同濃度一氧化碳的氫氣進料時，隨著一氧化碳濃度升高電池性能會有明顯的衰退，這是因為白金觸媒被毒化的程度與一氧化碳濃度呈正比關係；另外，觸媒受毒化的程度也與受毒化時間長短呈正比關係。又升高電池溫度有利於一氧化碳從白金觸媒上脫附而使毒化影響減低。
關鍵字
質子交換膜燃料電池並列摘要
The study contains two parts and the purpose is to improve the performance of PEMFC. The first part is focused on the cathode fabrication parameters such as ratio of Nafion and PTFE in catalyst layer, weight percentage of Pt/C catalyst, the membrane hot-press pressure, and thickness of membrane. The cathode with a fixed Platinum loading of 0.4mg/cm2 was prepared by the decal method, and all electrochemical experiments were carried out at 60℃ under ambient pressure. In the half cell test system, 1M H2SO4 was used to provide H+, and 65c.c./min of oxygen was supplied while measurements were proceeded. The results show that cathodes prepared by both 10wt% Pt/C and 20wt% Pt/C can reach their best performance beyond 1.5 A/cm2 at applied potential at 0.1V where catalyst layer contains 5wt% PTFE and the weight ratio of Pt/C to Nafion is 0.1. As the weight percentage of PTFE increases, however, the performance of cathode prepared by 10wt% Pt/C decays while the performance of cathode prepared by 20wt% Pt/C sustains. Moderate pressure at 100kg/cm2 is most suitable for membrane hot-press to achieve the best performance. Cathode that applied with Nafion 117 membrane has better performance than Nafion 112 , and no membranes due to its stronger resistance to the penetration of sulfuric acid. The second part is to investigate the external operating parameters of PEMFC including cell temperature, humidified temperature, flow rate and compositions of feeding gas. MEA applied here was prepared by brush method with platinum loading 0.4mg/cm2 for both anode and cathode, and the total amounts of Nafion ionomer in the electrodes have been fixed as half of the Pt/C weights. The electrolyte membrane and diffusion layer applied here were Nafion 117 and 20wt% wet-proofed carbon paper, respectively. The results show that cell performance is enhanced with increasing cell temperature, but humidified temperature of feeding gas still needs to be considered to achieve better performance. When 300c.c./min of pure hydrogen is fed at anode, cell performance goes steadily up with an increased oxygen flow rate until 300c.c./min. Using air instead of oxygen as cathode feed, cell performance decays due to the oxygen starvation since air contains only 20% oxygen. A trace amount of CO in the hydrogen gas feed poisons platinum catalyst and causes cell performance down. Besides CO concentration, cell performance is declined along with the poisoning time. Raising cell temperature can help CO desorb from platinum surface and improve cell performance.
並列關鍵字
PEMFC參考文獻
1. J. M. Leger., and C. Lamy, Ber. Bunsenges. Phys. Chem. 94, 1021(1990).
4. J. Larminie and A. Dicks, “Fuel Cell Systems Explaind”, John Wiley & Sons, Inc., 2000.
5. L. Giorgi, E. Antolini, A. Pozio, E. Passalacqua, Electrochim. Acta, 43,3675-3680 (1998).
6. C. Lim, C.Y. Wang, Electrochim Acta , 49, 4149-4156 (2004) .
7. V. Jalan, E. J. Taylor, J. Electrochem. Soc., 130, 2299(1983).