With zero emission when using hydrogen as fuel and air as oxidant, polymer electrolyte membrane fuel cells (PEMFC) are most promising for vehicle, portable and stationary applications (1, 2). Nevertheless, high-cost and improvable durability are well-known so major goals for development of PEMFC are low-cost, high performance and excellent durability (3). Important components are membrane electrode assembly (MEA), where the electrochemical reactions take place, and bipolar plates (BPP), which are designed to distribute fuel gas and air, remove heat and insure current flow from cell to cell (3, 4). Here, the influence on the efficiency and corrosion issues with the material is already known (5). Due to that fact, the effect on durability of materials and the whole stack are investigated in this work focusing on the ex-situ analysis of stack components like BPP to get information about the effects of gas flow, temperature or position of the individual cells. The test duration is 500 h at constant load of 0.31 A cm^-2 at 160°C. Before and after this test polarization curves are recorded to identify the effect on the performance of the stack. Moreover, water samples are collected on anode and cathode side during operation of test to analyze the acid content via titration and ion chromatography. In addition, the content of acid of the MEA and BPP after the test will be investigated. Since phosphoric acid is used as electrolyte in PEMFC the content of acid in the components can be used to investigate the influence of acid loss during the test. The degradation is examined at various points in the stack, e.g. at gas inlets and outlets of the bipolar plate. Also, the surface roughness of bipolar plates will be determined with confocal microscopy. Deeper changes in structure in MEA and BPP will be analyzed with micro-computed tomography.

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