Investigation of the transversal water profile in nafion membranes in polymer electrolyte fuel cells
Investigation of the transversal water profile in nafion membranes in polymer electrolyte fuel cells
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DOI：
10.1149/1.1345868
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发表时间：
2001-03-01
影响因子：
3.9
通讯作者：
Scherer, GG
中科院分区：
文献类型：
--
作者：
Büchi, FN;Scherer, GG
在一维燃料电池中测量了不同厚度的Nafion膜的电阻随电流密度的变化。在0 ~ 1A/cm（2）范围内，除薄的Nafion 112膜外，离子电阻随电流密度的增大而增大，在相同的电流密度区间内，膜越厚，增大的幅度越大。通过使用由多个薄片组成的膜，其中夹有细金线作为电位探针，来确定跨膜厚度的电阻分布。发现电阻的增加总是局限于与阳极电极接触的膜片。这些测量结果，与不同的水含量的膜的实验结果相结合，导致的结论是，在阳极侧的电阻增加是由于不充分的补偿的电渗透阻力的水回输到阳极。基于水在膜中运动的溶液扩散机制，实验结果可以通过电渗透阻力系数与局部膜水合无关和水扩散系数D-H2O是局部膜含水量的强函数的机制来解释。实验数据也将定性地与提出通过膜的亚微孔中的水的对流将水反向输送到阳极的模型一致。(C)2001年电化学学会。All rights reserved.
The in situ resistance of Nafion membranes with different thickness was measured in one-dimensional fuel cells as a function of current density. Except for the thin Nafion 112 membrane, an increase of the ionic resistance with current density tin the range 0 to 1 A/cm(2)) was found. The thicker the membrane, the stronger the increase in the same current density interval. The resistance distribution across the thickness of membranes was determined by using membranes composed from several thin sheets with interlying thin gold wires as potential probes. It was found that the increase of the resistance is always confined to the membrane sheet contacting the anode electrode. These measurements, combined with the results from experiments with membranes of different water content, lead to the conclusion that the resistance increase at the anode side is due to the insufficient compensation of the electro-osmotic drag by the back transport of water to the anode. Based on a solution diffusion mechanism of the water motion in the membrane, the experimental results may be explained by a mechanism whereby the electro-osmotic drag coefficient is independent of the local membrane hydration and the water diffusion coefficient D-H2O, is a strong function of the local membrane water content. The experimental data would, qualitatively, also be in line with a model proposing back transport of water to the anode by convection of water in the submicropores of the membrane. (C) 2001 The Electrochemical Society. All rights reserved.