|Abstract: ||現今，燃料電池科技做為替代能源已經受到相當大的關注。燃料電池像一般電池一樣可以將化學能轉換成電能。不同的燃料電池規格及系統設計被使用於不同的應用方面，在所有的燃料電池中，質子交換膜燃料電池 (PEMFC)能產出大量的能量，這可使 PEMFC應用在車輛上。本研究主要是在氬氣氣氛下，利用脈衝雷射法 (PLD)去沉積白金 (Pt)奈米顆粒於氣體擴散層 (GDL)上。主要分成兩種方法去調整 GDL，第一種方法是用滴定鑄造法將 Nafion滴在 GDL上，來改善質子傳導 ;而第二種方法是藉由雷射為加工將 GDL的觸媒表面積提升。 |
在第一種方法中，改變 Nafion離聚物的含量滴定鑄造在 GDL上的影響。當加入Nafion離聚物於觸媒漿料裡，可以改善質子傳導。首先 Pt觸媒會沉積在 GDL上，之後再將 Nafion溶液滴定鑄造在 GDL上，不同的 Nafion濃度藉由不同水及乙醇的濃度而被稀釋。結果顯示，基板及溶液的濕潤性在達到最大電流密度下扮演著極為重要的角色。在低 Pt擔載量為 100 μg cm−2時，最佳化 Nafion、水及酒精濃度分別為
0.05 wt%、33.5 wt%及 66.5 wt%。在另一方面，在高 Pt擔載量為 200 μg cm−2時，最佳化 Nafion濃度約為 0.025 wt%，更進一步檢測會被用來鑑定滴定鑄造法。
在第二種方法中，雷射微加工基板的結果顯示，藉由增加 Pt擔載量，能量密度不會下降。增加 Pt擔載量會提升膜厚，進而影響燃料電池性能。首先，使用皮秒雷射在GDL表面上製備凹槽來提升有效 Pt表面積沉積，並且降低 Pt膜厚，之後利用 PLD將 Pt沉積在觸媒上。藉由雷射微加工能製備出 20微米寬及 10微米深的凹槽，能量密度在 0.6 V下達到 853 mW cm−2，陰極 Pt擔載量為 200μg cm−2。假如能藉由改善雷
;Recently, fuel cell technologies have received much attention as an alternative energy source. Fuel cells are like batteries that convert chemical energy into electricity. Different specifications and system design of the fuel cells are required for different applications. Among all the fuel cells, PEM fuel cell produces the most power for a given volume of the
fuel cell, which makes them suitable for vehicles. In this study, pulsed laser deposition (PLD) in Ar atmosphere was used to deposit Pt nanoparticles on the gas diffusion layers (GDLs). There were two methods of tailoring the GLDs have been explored in this study.
The first method is to improve the proton transport by drop casting Nafion on the GDL. The second topic is centered on increasing the surface area of the catalyst by laser micro-machining the GDL.
On the first method, the influence of Nafion® ionomer content drop casted on the GDL was investigated. The addition of Nafion® ionomer content in the catalyst ink enhances the proton conduction. In our study, Nafion® ionomer content is separately deposited on the GDL. The Pt was first deposited on the GDL and afterwards drop casted by Nafion® solution. Different Nafion® concentrations were diluted in different concentrations of water and ethanol. Results showed that the wettability of the substrate and the solution play a great role in achieving the highest current density. At lower Pt loading, 100 μg cm2, the optimized Nafion®, water, and ethanol concentration were 0.05 wt%, 33.5%, and 66.5%,
respectively. On the other hand, at higher Pt loading, 200 μg cm2, the optimized Nafion® concentration was 0.025 wt%. Further characterizations are needed to quantify the drop casting method.
The second method include laser micro-machining the substrate. Laser-micromachining the substrate demonstrate that by increasing the Pt loading the power density does not drop. Increasing the Pt loading increases the film thickness which affects the fuel cell performance. Firstly, the picosecond laser fabricates grooves on the surface of the gas diffusion layer to greatly increase the effective surface area of Pt deposition, thereby re-
ducing the Pt film thickness. And, secondly, pulsed laser deposition was used to deposit the Pt on to the catalyst. A 2-fold increase in the maximum power density is achieved by using laser micro-machined periodic grooves of 40 μm period, 20 μm groove width, and 10 μm depth, reach 853 mW/cm2 and a maxmimum power density of 1.2 mW/cm−2 with a cathode Pt loading of 200 μg/cm2 . Further promotion is expected if the groove width and the period could be reduced by improving the laser micro-machining process.