Effects of purging on the degradation of PEMFCs operating with repetitive on/off cycles

Degradation of polymer electrolyte membrane fuel cells (PEMFCs) that is facilitated by on/off cycles is one of the most important issues for commercialization of fuel cell vehicles. When a PEMFC stack is shut down, residual hydrogen could induce high voltage equivalent to open-circuit voltage to the cathode side that might cause sintering of the Pt catalyst and facilitate the formation of hydrogen peroxide radicals at the anode side that might decompose the Nafion membrane. In this study, the degradation of PEMFCs exposed to repetitive on/off cycles was investigated by measuring current density-voltage characteristics, ac impedance, cyclic voltammograms, gas leak, cross-sectional scanning electron microscopy images, and transmission electron microscopy images. To prevent the degradation of PEMFCs caused by the residual gases, hydrogen was removed from the anode gas channel by air-purging, which was found to be a very effective method. (c) 2006 The Electrochemical Society. All rights reserved.