High temperature PEMFCs based on phosphoric acid‐doped ABPBI membranes have been prepared and characterised. At 160 °C and ambient pressure fuel cell power densities of 300 mW cm–2 (with hydrogen and air as reactants) and 180 mW cm–2 (with simulated diesel reformate/air) have been achieved. The durability of these membrane electrode assemblies (MEAs) in the hydrogen/air mode of operation at different working conditions has been measured electrochemically and has been correlated to the cell resistivity, the phosphoric acid loss rate and the catalyst particle size. Under stationary conditions, a voltage loss of only –25 μV h–1 at a current density of 200 mA cm–2 has been deduced from a 1,000 h test. Under dynamic load changes or during start–stop cycling the degradation rate was significantly higher. Leaching of phosphoric acid from the cell was found to be very small and is not the main reason for the performance loss. Instead an important increase in the catalyst particle size was observed to occur during two long‐term experiments. At high gas flows of hydrogen and air ABPBI‐based MEAs can be operated at temperatures below 100 °C for several hours without a significant irreversible loss of cell performance and with only very little acid leaching.

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40Aims: To investigate whether arbuscular mycorrhizal fungi (AMF) -abundant in a 41 phosphate-polluted but nitrogen-poor field site -improve plant N nutrition, we carried out a 42 two-factorial experiment, including N fertilization and fungicide treatment.

Chromium poisoning of solid oxide fuel cell cathodes is up to now considered as one major factor which limits lifetime and is responsible for degradation. Still unclear is to what extent chromium poisoning is responsible and what the basic degradation mechanism is. At Forschungszentrum Jülich, this ambiguity is being clarified in two ways: firstly the post-mortem analysis of cells operated within a stack and secondly by carrying out single cell tests with varied chromium releasing sources and operating conditions. This paper summarizes the results of approximately 60 single cell tests. The experiments were carried out with variation of operation time, current density applied and the chromium source. The cells were characterized for their degree of degradation, for their chromium content and change in microstructure. The results show that cells solely degrade strongly when current density was applied and a strong chromium source was present, and support an electrochemical interaction mechanism.

Chromium poisoning of solid oxide fuel cell cathodes is up to now considered to be a major factor which limits life-time and is responsible for degradation. Still unclear is to which extend chromium poisoning is responsible for degradation and what the basic degradation mechanism is. The Forschungszentrum Jülich tries to clarify this ambiguity in two ways: firstly by post-mortem analysis of cells operated within a stack and secondly by carrying out single cell tests with varied single cell measurement equipment. This presentation summarizes the post-mortem characterization of approximately fifteen stack tests. The two major parameters varied were the applied current density during operation and the operation time. SEM micrographs and wet chemical analysis of the cell materials are presented. Up to now a direct correlation between deposited amount of chromium within the LSM cathode and the degradation rate of the stack could not be established.