直接甲醇燃料電池氣體擴散層之研究

The research of DMFC gas diffusion layer

宋政勳(Zheng--xun Song)

指導教授 ： 曾重仁

國立中央大學/工學院/能源工程研究所/碩士(2008年)

摘要

本文以刮塗法(scrapping method)來製備直接甲醇燃料電池(DMFC)之微孔層，再搭配自製之疏水碳布和商用疏水碳紙做為 DMFC 之氣體擴散層，利用以 PTFE 為主之疏水性微孔層與以 Nafion 為主之親水性微孔層，藉由陰、陽極端不同的實驗參數規劃，找出能使 DMFC發揮最高性能之微孔層與氣體擴散層之組合。
與PEMFC最大不同處，一般 DMFC 陽極端微孔層跟氣體擴散層之設計除了能幫助甲醇水溶液能均勻、順利地供給陽極端觸媒使用，還需考慮能將陽極所產生之二氧化碳順利地由陽極微孔層和氣體擴散層排除，使觸媒能發揮最大功效。大部份研究顯示，陽極使用親水性微孔層與以疏水碳布為主之氣體擴散層、陰極使用疏水微孔層和疏水碳布之氣體擴散層，能使 DMFC 發揮較佳性能。
本研究結果顯示，當陽極供給較大流量之甲醇水溶液(6 ml/min)與較低濃度(1.18M)時，反而是陽極端使用20 wt% PTFE 含量之疏水性微孔層，陰極端使用60 wt% PTFE 含量之疏水性微孔層，再搭配10 wt% PTFE 含量疏水碳布作為氣體擴散層能使電池達最大性能，在0.27V時，電流密度達274 mA/cm2、功率密度74.9 mW/cm2，此時陽極端碳黑負載量為1.87 mg/cm2、陰極端碳黑負載量為1.12 mg/cm2。

關鍵字

DMFC ； 微孔層 ； 氣體擴散層

並列摘要

The purpose of this study is to investigate the effects of microporous layer (MPL) and gas diffusion layer (GDL) on the performance of direct methanol fuel cell (DMFC). Both carbon cloth and carbon paper are used as the GDL. The scrapping method is used to prepare the MPL. The MPL is made hydrophobic using PTFE and hydrophilic using Nafion. The effects of hydrophobic and hydrophilic treatment on cell performance are studied.
Unlike in proton exchange membrane fuel cells, the GDL and MPL in DMFCs need to provide the function of carbon dioxide removal as well as uniform fuel distribution. Most previous work shows that using a hydrophilic MPL with hydrophobic carbon cloth at anode and hydrophobic MPL with hydrophobic carbon cloth at cathode results in better DMFC cell performance.
Results of this work show that, for the condition used in this study, using 20 wt% PTFE hydrophobic MPL at anode and 60 wt% PTFE hydrophobic MPL at cathode with 10 wt% PTFE hydrophobic carbon cloth as the GDL at both anode and cathode exhibit the best cell performance. The carbon black loading in this case is 1.87 mg/cm2 at anode MPL and 1.12 mg/cm2 at cathode MPL. The current density reaches 274 mA/cm2 and the power density reaches 74.9 mW/cm2 at 0.27 V and 50℃.

並列關鍵字

DMFC ； gas diffusion layer ； microporous layer

參考文獻

3. K.T. Jeng, S.F. Lee, G.F. Tsai, C.H. Wang, ”Oxygen mass transfer in PEM fuel cells gas diffusion layers,” Journal of Power Source, 138, 41-50, 2004.

4. J. Benziger, J. Nehlsen, D. Blackwell, T. Brennan, J. Itescu, ”Water flow in the gas diffusion layer of PEM fuel cells,” Journal of Membrane Science, 261, 98-106, 2005.

5. H.K. Lee, J.H. Park, D.Y. Kim, T.H. Lee, ”A study on the characteristics of the diffusion layer thickness,” Journal of Power Source, 131, 200-206, 2004.

6. A. Oedegaard, C. Hebling, A. Schmitz, S. Møller-Holst, R. Tunold, ” Influence of diffusion layer properties on low temperature DMFC,”

Journal of Power Sources 127, 187–196, 2004.