Membrane degradation mechanism during open-circuit voltage hold test

A detailed analysis is made of the relation between the degradation behavior of a membrane electrode assembly (MEA) and deposited Pt (Pt band) in the membrane during an open-circuit voltage (OCV) hold test. Molecular-structural changes in the membrane are investigated by micro-Raman spectroscopy. When the Pt band was not significantly observed in the membrane after the test, the membrane is relatively stable. In contrast, when the Pt band was clearly formed, the membrane around it was intensively degraded. The magnitude of the fluoride ion emission rate (FER) of the effluent water from the anode and the cathode was also consistent with the location of the Pt band. It was verified that the Pt band is one of the factors accelerating membrane degradation, and the catalyst materials strongly affects the degradation. Besides, not the cation transport which enhances the degradation but the kinetics of either the H2O2 and/or hydroxyl radical production might be the rate determining step. (c) 2008 Elsevier B.V. All rights reserved.