Influence of Operating Parameters on Start/Stop Induced Degradation in Polymer Electrolyte Fuel Cells

In order to investigate the influence of temperature, reactant gas humidification and the application of an auxiliary load on start/stop induced fuel cell degradation under application relevant conditions, alternating purging of the anode electrode with hydrogen (on state) and air (off state) was used to shut-down and start-up the fuel cell. It was found that loss of active catalyst surface area only significantly influences fuel cell performance at low temperatures and reactant gas humidifications. Under harsh conditions, performance decrease is dominated by mass transport losses which are caused by carbon corrosion induced changes in the structure of the catalyst layer. Measurements of the CO2 content in the cathode exhaust gas showed that carbon corrosion rate depends linearly on water vapor partial pressure. Up to 80°C, temperature does not additionally influence carbon corrosion. Due to a strongly increased driving voltage and the longer duration of the detrimental potential, performance loss was dramatically increased in case of the fuel cell cycled without auxiliary load.