Influence of the composition on the structure and electrochemical characteristics of the PEFC cathode
Influence of the composition on the structure and electrochemical characteristics of the PEFC cathode
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DOI：
10.1016/s0013-4686(03)00603-0
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发表时间：
2003-12
影响因子：
6.6
通讯作者：
P. Gode;Frédéric Jaouen;G. Lindbergh;Anders Lundblad;G. Sundholm
中科院分区：
文献类型：
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作者：
P. Gode;Frédéric Jaouen;G. Lindbergh;Anders Lundblad;G. Sundholm
针对10至70wt%的Nafion含量，研究了阴极组成对其结构和电化学性能的影响。阴极通过喷涂法在Nafion膜上形成，并使用20wt. %的Vulcan（E-TEK）上的Pt。材料表征（SEM，STEM，气体和汞孔隙率，电子电导率）和电化学表征（稳态极化曲线，阻抗谱在O2和电流脉冲测量在N2）进行。使用我们的动态凝聚模型的阻抗谱进行了分析。结果表明，团聚体模型是有效的，直到约45wt. %的Nafion含量。Pt/C和Nafion对于任何组合物均匀混合，并且没有观察到Nafion膜。阴极含有36 - 43wt. % Nafion显示出单或双塔菲尔斜率行为归因于团聚体中的扩散限制。在较大的Nafion含量，团聚体模型可以描述的曲线只有假设一个扩散系数3 - 4个十年小于气体。在这样的组成下，孔隙率仅为10%。这些结果被解释为阻塞的孔隙和非膨胀的孔隙系统太大的Nafion含量。
The influence the composition of the cathode has on its structure and electrochemical performance was investigated for a Nafion content spanning from 10 to 70wt.%. The cathodes were formed on a Nafion membrane by the spray method and using 20wt.% Pt on Vulcan (E-TEK). Materials characterisation (SEM, STEM, gas and mercury porosimetry, electron conductivity) and electrochemical characterisation (steady-state polarisation curve, impedance spectroscopy in O2and current-pulse measurements in N2) were performed. The impedance spectra were analysed using our dynamic agglomerate model. The results indicate that the agglomerate model is valid until a Nafion content of about 45wt.%. Pt/C and Nafion are homogeneously mixed for any composition and no Nafion film was observed. The cathodes containing 36–43wt.% Nafion display a single or double Tafel slope behaviour ascribed to diffusion limitations in the agglomerates. At larger Nafion content, the agglomerate model can describe the curves only by assuming a diffusion coefficient 3–4 decades smaller than that of gases. At such compositions, the porosity was only 10%. These results were interpreted as a blocking of the pores and a non-percolating pore system for too large Nafion contents.