氧氣端電極觸媒物種對URFC特性之研究

Effect of oxygen electrode catalysts on unitized regenerative fuel cell

卓敏貴(Min-Guei Juo)

指導教授 ： 蘇艾

共同指導教授 ： 鐘國濱

元智大學/工程學院/機械工程學系/碩士(2006年)

https://doi.org/10.6838/YZU.2006.00126

摘要

一個良好的均一化再生型燃料電池（URFC）性能，決定於適當的電極結構與最佳的操作溫度，本文主要之目的是在探討觸媒與溫度對於水電解反應與燃料電池系統之影響。不同的電極觸媒材料會影響電極電化學反應的效率，不同電極材料電位對電化學反應速率的影響程度有著顯著的不同。適用於水電解之電極觸媒未必能適用於燃料電池系統，選擇此種複合式的觸媒是一項重要且不容易之工作。
對於氧氣端電極而言，50wt％Ir+50wt％Ru是最佳的水電解合金觸媒，電極中添加Pt與Ir皆可以提昇電解之效能。觸媒為IrRu時，其最佳之操作溫度為60度∼80度。調昇電池之溫度，可減少電解所需之能量，並增加觸媒之活性，加快其反應速率。分析觸媒之導電度得知，觸媒之活性影響大於觸媒金屬之導電度。溫度之增加可觸進觸媒活性的提昇，加速水電解之化學反應，並可增大觸媒金屬之導電度，使得水電解性能大幅增加。
觸媒為Pt有助於提昇燃料電池之效能，研究發現性能提高，伴隨溫度之增加。MEA操作於高溫下，高溫條件會促使電解質薄膜加快劣化，燃料水分加濕不足，MEA可能會過乾，薄膜會因失去水分造成電池質傳極限，反應氣體燃料水分不足影響電池性能。80度時會使燃料電池系統之膜電極組的水分不足，造成膜的乾化，阻礙離子之傳遞，使得效能不穩定的降低。燃料電池最佳的操作溫度為60度。
在燃料電池與水電解系統中皆需要導電度良好之觸媒，一般會在電池觸媒中加入導電性佳的碳粉，本實驗使用含碳之PtRu觸媒，探討含碳量對性能之影響。
URFC系統裡不可有碳的成份存在，其原因為碳在水電解時會破壞氧氣端的電極，碳會被電解析出，污染電解液使其性能無法提昇。

關鍵字

均一化再生型燃料電池 ； 觸媒 ； 水電解

並列摘要

A satisfactory performance of an electrolytic battery is achieved with the electrode structure and the best operation temperature. The main purpose of the paper discusses the influence of catalysts and temperature on electrolytic response of water. The best candidate catalyst for fuel cell might be improper for electrolysis. It is an important and difficult work to choose the bifunctional electrodes with a thin catalyst layer.
50wt.% Ru + 50wt.% Ir is a good bifunctional catalyst for the oxygen electrode. By adding Pt and Ir in the catalyst increase the electrolytic efficiency. When the catalyst is IrRu, its best operation temperature is spent for 60℃~80℃. Adjust and rise the temperature of the cell, can reduce electrolytic energy, increase the activation of the catalyst, and accelerate speed of response. Analyse electric conduction of catalyst can know that the active influence of the catalyst be better than electric conduction of the catalyst metal. Increasing the temperature can improve the activation of catalyst, accelerate the electrolytic chemical reaction of water, and can increase electric conduction of the catalyst metal, make the electrolytic performance of water increase.
The high-temperature condition will impel the electrolyte membrane to accelerate decay. When the moisture humidification of the fuel is not enough, MEA may be too dry, the membrane will because lose moisture cause the cell mass transfer polarisation. When temperature is 80 ℃, make the moisture of the membrane electrode group insufficient of fuel cell, cause the dryness of the membrane, hinder the transmission of the ion, and make efficiency unstable and drop. The best operation temperature of the fuel cell is 60 ℃.
The fuel cell and electrolysis system need conductibility good catalyst. Usually join the carbon powder of good electric conductivity in the electrode catalyst. This experiment uses the PtRu catalyst includes of the carbon, probe for the influence on performance of carbon content. So we must experiment the URFC system without carbon, because the carbon will destroy the electrodes of the oxygen end when water is electrolytic, the carbon will be appeared electrolytically, and the electrolytic liquid of pollution makes its performance unable to promote.

並列關鍵字

URFC ； electrolysis ； catalyst ； conductibility

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