Journal
JOURNAL OF POWER SOURCES
Volume 422, Issue -, Pages 163-174Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jpowsour.2019.03.001
Keywords
Polymer electrolyte membrane fuel cell; Membrane hydration; Water crossover; High current density; Electrochemical impedance spectroscopy; Synchrotron X-ray radiography
Funding
- Automotive Fuel Cell Cooperation Corp. (AFCC)
- Natural Sciences and Engineering Research Council of Canada Canada Discovery Grants Program
- NSERC Discovery Accelerator Program
- NSERC Canada Research Chairs Program
- Canada Foundation for Innovation
- Mitacs Accelerate Program
- Friends of Ara Mooradian Scholarship
- William Dunbar Memorial Scholarship in Mechanical Engineering
- Mercedes-Benz Canada Graduate Fellowship in Fuel Cell Research
- NSERC Canada Graduate Scholarship (CGS-M)
- Ontario Graduate Scholarship (OGS)
- David Sanborn Scott Fellowship
- University of Toronto Connaught International Scholarship for Doctoral Students
- Ron D. Venter Fellowship
- Hatch Graduate Scholarship
- Pierre Rivard Hydrogenics Graduate Fellowship
- Natural Sciences and Engineering Research Council of Canada
- Canadian Institutes of Health Research
- Government of Saskatchewan
- Western Economic Diversification Canada
- University of Saskatchewan
- CLS Post-Doctoral and Graduate Student Travel Support Program
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The membrane hydration state of a polymer electrolyte membrane fuel cell is investigated in operando at high current densities (> 1.5 A cm(-2)) for various inlet gas relative humidities (RH). The ohmic resistance, an indicator for membrane hydration, is found to have a non-monotonic dependence on current densities between 0 and 3.0 A cm(-2), and the current density corresponding to the local minimum ohmic resistance is defined as the optimal hydration current density. While the relative thickness of the membrane increases with increasing inlet RH, an interesting observation was made whereby elevating the catalyst-coated membrane (CCM) temperature at current densities above the optimal hydration current density leads to membrane dehydration. Surprisingly, at high inlet gas RH values (70% and 100%) and high current densities, membrane dehydration results in membrane shrinkage (relative to its thickness at 0 A cm(-2)). We attribute the membrane dehydration and associated shrinkage to the reduced local RH at the CCM, even though the net water flux from the cathode to anode increases. The relative membrane thicknesses as a function of inlet RH conditions are determined from the low frequency arc time constants obtained via electrochemical impedance spectroscopy measurements.
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