Morphology studies on high-temperature polymer electrolyte membrane fuel cell electrodes

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• 作者：Florian Mack ; Merle Klages ; Joachim Scholta ; Ludwig J枚rissen ; Tobias Morawietz ; Renate Hiesgen ; Dominik Kramer ; Roswitha Zeis
• 关键词：HT-PEM ; PBI doped with phosphoric acid ; X-ray microtomography ; Atomic force microscopy (conductive mode) ; Electrode morphology ; Electrode preparation
• 刊名：Journal of Power Sources
• 出版年：1 June, 2014
• 年：2014
• 卷：255
• 期：Complete
• 页码：431-438
• 全文大小：2402 K

文摘

The electrode morphology influences the properties and performance of polymer electrolyte membrane fuel cells (PEMFC). Here we report our studies of two different electrodes for high-temperature PEMFC prepared by spraying and coating and their impact on the fuel cell performance. Differences in 3D microstructure and adhesion between catalyst layer and gas diffusion layer (GDL) of the electrodes were studied with X-ray microtomography. Scanning electrode microscope investigations show hairline cracks between agglomerates on the surface of the sprayed electrode, whereas the coated electrode shows a network of shrinkage cracks in the catalyst layer. The distribution of the electrode binder polytetrafluoroethylene (PTFE) is related to the locally resolved conductivity, which was determined by scanning the electrode surfaces with a conductive atomic force microscopy (AFM) tip. The macrostructures of the sprayed and coated electrodes are different but contain similar pore structures. The coated electrode has a higher PTFE concentration on the top region, which tends to form a nonconductive and less wettable 鈥渟kin鈥?on the electrode surface and delays the start-up of the fuel cell. In contrast to low-temperature PEMFC, the electrode morphology has only a minor impact on the steady-state cell performance of high-temperature PEMFC.