矽基材及高分子材微型質子交換膜燃料電池之設計與性能分析

Abstract

本論文主要分為兩部分。第一部分主要是研究以微機電製程製作矽基材微型質子交換膜燃料電池之實驗測試。首先設計流道的光罩，接著利用微機電製程：物理氣相沉積、化學氣相沉積、上光阻、曝光、顯影、乾蝕刻、濕蝕刻，製作出我們所設計的流場板。然後進行組裝微型燃料電池零件：壓克力端板、流場板、集電板、防漏墊片、氣體擴散層、質子交換膜包括觸媒層及其反應面積為2公分×2公分。組裝完成後，進行燃料電池測試。測試參數包括有: 流場板的開孔率、集電片的接觸面積、集電片的材質以及不同之氧化劑供應。實驗結果顯示，集電片的接觸面積和材料對於微型燃料電池之性能有很大的影響，尤其是前者。流場板開孔率75%相較於開孔率為50與67%有最佳的性能曲線；增加陰極的空氣流量，可以改善高電流密度情況下的濃度極化現象。此外長時間的測試下，在各種不同操作電壓下經10小時後能保有穩定的功率輸出。 第二部分則以微製程中的乾蝕刻製程製作微型PDMS質子交換膜燃料電池。首先針對單電池之性能實驗。此部分包含集電片開孔形狀、對流方式、以及組裝時鎖合壓力的影響；其次為設計製作PDMS平板電池堆之研究，實驗參數包括鎖合扭力以及燃料供應方式的影響；另外，單電池及電池堆都經由長時間放電測試以觀察其耐久度。由實驗結果可知在相同開孔率之集電片下，不論陰極採用呼吸式或是強制對流式之單電池，在固定集電片開孔率時其性能皆隨著開孔數增加而提升；強制對流方式的單電池比較適合長時間高電流密度輸出使用，而呼吸式燃料電池較適合低電流密度輸出使用；電池組裝之鎖合壓力必須在不使流道結構變型的情況下增加才能有效提升其性能；對於本實驗之電池堆設計，由於陰極端的空氣提供速率有限，因此增加燃料流量並無法有效改善濃度極化現象；實驗中也應用了熱顯像儀觀察電池堆之溫度變化，發現電池堆中因為每一顆電池排列順序不同而會有不同性能表現；單電池與電池堆經過14小時長時間測試後，都能保有穩定的輸出。 最後，本論文也將PDMS微型燃料電池與矽基材微型燃料電池做性能的比較。不論陰極採用呼吸式或是強制對流式，PDMS基材之單電池皆比矽基材之單電池性能表現佳；由於PDMS基材有較高的絕熱性能加速蒸發電池內部之積水現象。

The dissertation consists of two parts. Part one utilizes Micro- electromechanical Systems (MEMS) technology to fabricate micro Si-based proton exchange membrane fuel cell (PEMFC) and followed by carrying out a series experiments. It designs masks firstly, then, uses MEMS technology to fabricate the flow field plate. The processes include physical vapor deposition (PVD) and chemical vapor deposition (CVD), coating photo resist (PR), exposure, development, dry and wet etching. Finally, assemble the components, such as acrylic end plates, flow field plates, collector plates, gaskets and gas diffusion layer (GDL) into a cell. The active area of the membrane-electrode-assembly (MEA) is 2cm×2cm. The parameters include open ratio of flow field plates, conducting area of current collector, material of current collector and different cathode gases, respectively. The experimental results show that both the conducting area and material of current collector slices have great influence on the performance of micro PEMFC, especially the former one. The performance is better for open ratio 75% compared with those of 50 and 67%. The concentration polarization is improved by increasing the air flow rate at high current densities. Furthermore, the performance at difference operating voltages can maintain a stable power output for a long time use up to 10 hours. Part two uses dry etching process of MEMS to fabricate micro PDMS-based (Polydimethyl Siloxane) PEMFC. A series of performance experiments on a single micro PDMS PEMFC was carried out firstly. The experimental parameters included current collector shape, convection type and clamping force, respectively. Secondly, a planar PDMS-based PEMFC stack was designed and assembled to test the performance. In this test, the parameters consisted of clamping force and fuel supply condition. In addition, both the single cell and stack were tested for durability. The experimental results showed that both the performances of the air-breathing and forced convection cells increase with an increase of the circle number on the current collector under the same current collector open ratio; The forced convection cell is a better choice for long-time high current-density output, whereas the air-breathing cell is more suitable for lower current density output; An appropriate clamping torque should be considered carefully to enhance the performance but without narrowing down the fuel flow channels; The increase of flow rate is not a best way to improve the concentration loss in this air-breathing stack experiment because of the limiting air supply. Experiments also employed the thermal imager to observe the cell temperature. It was found that each cell in the same stack has different performance under series arrangement; Both the single micro PDMS fuel cell and the cell stack can maintain a stable power output for a long time use up to 14 hours. Finally, a comparison between PDMS-based PEMFC and Si-based one was made. The PDMS-based PEMFC has a better performance than that of the Si-based one under both the forced oxygen supply and air-breathing ways, because PDMS substrate with high thermal insulation can quickly evaporate the liquid water.