Ageing of PEMFC's due to operation at low current density: Investigation of oxidative degradation
Ageing of PEMFC's due to operation at low current density: Investigation of oxidative degradation
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DOI：
10.1016/j.ijhydene.2010.07.180
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发表时间：
2010-10-01
影响因子：
7.2
通讯作者：
Lapicque, F.
中科院分区：
文献类型：
--
作者：
Franck-Lacaze, L.;Bonnet, C.;Lapicque, F.
本文旨在研究PEMFC在电流循环下的老化：在额定条件下(540 mA cm(-2))的工作周期之后是低电流密度(120或20 mA cm(-2))，循环的两个阶段都是长达一小时的周期。在单个25厘米(2)FC中的MEA逐步老化之后，通过监测电池电压、在不同测试周期结束时的阻抗谱以及通过分析所收集的水组分来进行。在120 mA cm(-2)下的老化强度降低，这是由等效单元电路的各种电阻的微弱增加所证实的，而在20 mA cm(-2)下重复操作则导致严重得多的退化。长期测试后的MEA的电子显微镜照片显示，全氟磺酸盐聚合物的大部分铂从阴极溶解和重结晶的重要性证实了这一点。此外，膜中硫的损失几乎不受老化过程的影响，而氟的损失在20 mA cm(-2)时是120 mA cm(-2)时的4倍：低电流密度所允许的高阴极电位可能改变聚合物链的分解机理，本文对此进行了讨论。(C)2010年，T.Nejat Veziroglu教授。爱思唯尔有限公司出版。保留所有权利。
The paper was aimed at investigating PEMFC ageing upon current cycling: periods of operation under nominal conditions (540 mA cm(-2)) were followed by periods at low current density (120 or 20 mA cm(-2)), the two phases of the cycles being hour-long periods. The progressive ageing of the MEA in the single 25 cm(2) FC was followed by monitoring the cell voltage, impedance spectroscopy at the end of the various test periods, and by analysis of the water fractions collected. Ageing at 120 mA cm(-2) was shown to be of reduced intensity as confirmed by the weak increase in the various resistances of the equivalent cell circuit, whereas repeated operation at 20 mA cm(-2) resulted in far more severe degradation. This was confirmed by the significance of Pt dissolution from the cathode and recrystallisation in the bulk of the perfluorinated sulfonate polymer, as revealed by TEM photographs of the MEA after the long-term tests. Besides, the loss of sulfur from the membrane was shown to depend little on the ageing procedure, whereas the loss of fluorine was four times larger at 20 mA cm(-2) than at 120 mA cm(-2): the high cathode potential allowed by the lower current density might change the decomposition mechanism of the polymer chain, as discussed in the paper. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.