Local degradation effects in automotive size membrane electrode assemblies under realistic operating conditions
| Autor: | Markus Perchthaler, Laurens Hallitzky, Tim Lochner, Aliaksandr S. Bandarenka, Michael Obermaier, Simon Enz, Jarek P. Sabawa |
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| Rok vydání: | 2019 |
| Předmět: |
Materials science
020209 energy Mechanical Engineering Proton exchange membrane fuel cell 02 engineering and technology Building and Construction Management Monitoring Policy and Law Electrochemistry Cathode Anode law.invention ddc General Energy 020401 chemical engineering law Electrode 0202 electrical engineering electronic engineering information engineering Relative humidity 0204 chemical engineering Current (fluid) Composite material Current density |
| Popis: | In automotive applications, the operational parameters for fuel cell (FC) systems can vary over a wide range. To analyze their impact on fuel cell degradation, an automotive size single cell was operated under realistic working conditions. The parameter sets were extracted from the FC system modeling based on on-road customer data. The parameter variation included simultaneous variation of the FC load, gas pressures, cell temperature, stoichiometries and relative humidity. Current density distributions and the overall cell voltage were recorded in real time during the tests. The current densities were low at the geometric anode gas outlet and high at the anode gas inlet. After electrochemical tests, post mortem analysis was conducted on the membrane electrode assemblies using scanning electron microscopy. The ex-situ analysis showed significant cathode carbon corrosion in areas associated with low current densities. This suggests that fuel starvation close to the anode outlet is the origin of the cathode electrode degradation. The results of the numerical simulations reveal high relative humidity at that region and, therefore, water flooding is assumed to cause local anode fuel starvation. Even though the hydrogen oxidation reaction has low kinetic overpotentials, “local availability” of H2 plays a significant role in maintaining a homogeneous current density distribution and thereby in local degradation of the cathode catalyst layer. The described phenomena occurred while the overall cell voltage remained above 0.3 V. This indicates that only voltage monitoring of fuel cell systems does not contain straightforward information about this type of degradation. |
| Databáze: | OpenAIRE |
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