Development of a Durable PEMFC Start-Up Process by Applying a Dummy Load II. Diagnostic Study

To investigate the effect of an application of a dummy load during the start-up procedure on the degradations of a membrane electrode assembly (MEA) exposed to the 1200 repetitive start-up-shutdown cycling, this paper uses a variety of physicochemical methods such as online CO2 analysis, field-emission-scanning electron microscopy, energy dispersive X-ray, electron probe microanalysis, X-ray diffraction, field-emission transmission electron microscopy, selected-area electron diffraction, X-ray photoelectron spectroscopy, Fourier transformation infrared, and inductively coupled plasma. After the 1200 start-up-shutdown cycles, a pronounced particle size growth/agglomeration/oxidation/dissolution of the Pt catalysts and corrosion of the carbon support were observed at the cathode catalyst layer when starting up a proton exchange membrane fuel cell (PEMFC) without a dummy load, which significantly contributed to the losses of active Pt surface area and Pt mass for electrochemical reactions, and thus the degradation of cell performance. However, applying a dummy load during the start-up procedure remarkably mitigated such severe degradations and should be used to improve the durability of MEAs during start-up-shutdown cycling of PEMFCs. Degradations at the anode and membrane were not as severe as those observed at the cathode. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3246003] All rights reserved.