Oscillations in the Gas Channels - The Forgotten Player in Impedance Spectroscopy in Polymer Electrolyte Fuel Cells A. Exploring the Wave
Oscillations in the Gas Channels - The Forgotten Player in Impedance Spectroscopy in Polymer Electrolyte Fuel Cells A. Exploring the Wave
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DOI：
10.1149/1.2356219
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发表时间：
2006-10
期刊：
影响因子：
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通讯作者：
I. Schneider;D. Kramer;A. Wokaun;G. Scherer
中科院分区：
文献类型：
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作者：
I. Schneider;D. Kramer;A. Wokaun;G. Scherer
我们的实验结果表明，在这里反驳，有限扩散一般可以假设在阻抗模型为H2/空气PEFC占氧气的扩散运输通过气体扩散层（GDL）向空气电极。它示出的氧浓度振荡的振幅创建作为叠加的AC电流在空气电极的结果，是不是在通道/GDL接口为零，但延伸到气体通道，至少低于调制频率fmod= 10 Hz。由此，阴极气体通道内的正弦氧气浓度振荡被局部地沿着流场激发。由于流场通道中的强制空气对流，在流场下游发生经由气相的耦合。耦合强烈影响的本地和由此的整体阻抗响应的细胞和唤起的H2/空气-PEFC阻抗谱中的低频电弧的形成。
Our experimental results shown here disprove that finite diffusion can generally be assumed in impedance models for H2/air-PEFCs to account for the diffusive transport of oxygen through the gas diffusion layer (GDL) towards the air electrode. It is shown that the amplitude of the oxygen concentration oscillation created as a consequence of superimposed ac current at the air electrode, is not zero at the channel/GDL interface, but extends into the gas channels, at least below modulation frequencies of fmod=10Hz. By this, sinusoidal oxygen concentration oscillations within the cathode gas channels are excited locally along the flow field. Due to the forced air convection in the flow field channels a coupling via the gas phase occurs downstream the flow field. The coupling strongly affects the local and by this the overall impedance response of the cell and evokes the formation of a low frequency arc in H2/air-PEFC impedance spectra.