直接塗佈製造技術對質子交換膜燃料電池膜電極組 性能之研究分析

Abstract

本研究著重於質子交換膜型燃料電池(PEMFC)的關鍵---膜電極組，包含膜電極組的組成零件、膜電極組(MEA)的製作方法以及測試的結果。在本論文中採用觸媒直接塗佈於質子交換膜上的作(CCM)。薄膜上的觸媒層緊密的與質子交換膜連結在一起，改善了觸媒層與質子交換膜中的接觸。 為讓MEA有最佳表現，必須決定流場板上流道的形式，流道形式以計算流學軟體-FLUENT進行分析，經過流場性質分析，以單蛇式流場(流道寬1.6mm、深度1mm、肋條寬1.35 mm)做為最終設計。 實驗先期在提升單電池的性能，經由改變塗佈方式、異丙醇用量、塗佈溫度、Dry Nafion薄層以及相對溼度等變因，希冀能掌握製作單一燃料電池的各項控制條件，以作為提升燃料電池堆性能的依據。文中針對各種變因所造成的性能差異，以電壓-電流曲線、SEM圖以及循環伏安法作為比較的指標，深入討論之。 膜電極組採用Nafion212，(反應面積50mm x 50mm)，當陰陽極觸媒量0.6mg/cm2、流量為0.25 SLM、氫氣和氧氣加濕70℃、電池操作溫度70℃時擁有最佳性能，在0.64V下，電流密度450.12 mA/cm2，產生0.29 W/cm2。 此研究也介紹了電池組的設計、製造與組裝，在電池組中包含了兩個電池，在1.2V時電流密度444.84 mA/cm2，產生0.53 W/cm2。 本文著重於MEA在不同於以往的製作方法中，觀察到對於MEA性能有所改善的方法，且試以將這些製程制式化，達到減少材料用量，則可對於燃料電池成本降低有所助益。

This study focuses on the key part of Membrane Electrode Assembly (MEA) - proton exchange membrane fuel cell, and also includes the component of the MEA; the manufacture method of the MEA and the test results. In this work, MEA were fabricated by catalyst coated membrane (CCM) method, the catalyst (Pt/C) was applied on the surface of membrane directly to improve the continuity of interface between the catalyst film and the membrane. To derive the best performance of MEA, the flow patterm needs to be verified by CFD software-FLUENT, the single serpentine type flow channel (channel width 1.6mm、deeth 1mm, rib width 1.35 mm) was chosen for the following tests. This study started from finding the way to improve the single-cell performance, according to the method of applying catalyst, amount of isopropyl alcohol, drying temperature, the presence of dry Nafion film and the relative humidity of inlet fuel. The results were verified by checking the overpotential curve (I-V curve), scanning electron microscope, cyclic voltammetry. Nafion212 was adopted as the membrane electrode assembly with an active area of 50 mm x 50 mm. The best performance of the home-made MEA was 0.29 W/cm2 at 0.64 V with power density of 450.12 mA/cm2, corresponding to the conditions as: Pt loading at cathode and anode side are both 0.6 mg/cm2, hydrogen and oxygen were at the same gas flow rate of 0.25 SLM, cell temperature at 70℃, and hydrogen andoxygen humidification temperature at 70℃. This study also introduced the design and manufacturing methods of a fuel cell stack. In this work, two cells were used to make a stack. The best output power was 0.53 W/cm2 at 1.2 V and 444.84 mA/cm2. The manufacture procedures in this study were different from others. We can find that some methods would improve the MEA performance. If we can make the procedure more general, or use less amount of material, then can reduce the fuel cell cost dramatically.