The response of polymer electrolyte membrane (PEM) fuel cells to a step change in load is investigated experimentally in this work. Voltage undershoot, a characteristic feature of transient response following a step increase in current, is due to transients of water distribution in the membrane and ionomers occurring at subsecond time scales. The use of humidified reactants as a means to control the magnitude of voltage undershoot is demonstrated. Further, the response under a step decrease in current density is explored to determine the existence of hysteresis. Under sufficiently humidified conditions, the responses under forward and reverse step changes are symmetric, but under low relative humidity conditions, voltage undershoot is twice as large as the overshoot. © 2009 The Electrochemical Society.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: Funding for this work from ECEC industrial sponsor is gratefully acknowledged. I. S. H. also acknowledges the King Abdullah University of Science and Technology (KAUST), Saudi Arabia, for a fellowship award.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.