In-situ EPR Spectroscopy - A Novel Method for the Investigation and Characterisation of the Membrane Degradation in PMFCs

摘要

This study comprises the development and application of electron paramagnetic resonance (EPR) electrochemistry techniques to study membrane degradation in Proton Exchange Membrane Fuel Cells (PEMFCs). The main aim thereby is a profound understanding of the degradation mechanisms and the identification of the fuel cell properties and operating conditions which assure durable and reliable performance of the membrane and fuel cell in general. In order to achieve it, a miniature fuel cell that can be operated in a resonator of an X-band EPR spectrometer was built. Two types of the fuel cell were investigated. The first one was equipped with commercial E-TEK Gas Diffusion Electrodes (E-TEK GDEs), the second one was a Membrane Electrode Assembly, prepared in the ITT DLR, Stuttgart (DLR MEA). The second type of the fuel ceil has no intrinsic signal and is therefore more suitable for the study of degradation processes. The spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was used at the cathode side of the cell equipped with a DLR MEA to observe the radicals originating from membrane degradation. After short time operation an EPR spectrum which is characteristic for an immobilised nitroxide radical was observed. The nature of the radicals is not yet clear and will be in the focus of further investigations.