Abstract
Interfacial contact resistance (ICR) is one of the remaining hurdles for successful implementation of stainless steel bipolar plates in PEM fuel cells. We have developed a reliable method, using thin gold wires, to measure the interfacial contact resistance between the bipolar plate material and the porous transport layer during fuel cell operation. The ICR values were found to be in the same range as the ICR values measured ex situ after fuel cell operation. Local ex situ ICR measurements on tested plates indicate uneven current distribution during fuel cell operation. Consequently, an average between three measuring points was used for the in situ measurements, which enabled consistent monitoring of the ICR development alongside fuel cell performance. For almost all of the tests, the largest ICR changes took place within the first two hours of operation, showing the importance of early ICR measurements. Non-coated stainless steel and titanium-coated steel BPPs experienced a higher ICR compared to the gold coated stainless steel.
Highlights
Proton exchange membrane fuel cells (PEMFCs) convert chemical energy to electrical energy, and are predicted to play an important role in the future sustainable society.[1]
In situ interfacial contact resistance measurements.—The cathode side was chosen for the in situ measurements as it is expected to experience the highest voltages and temperatures, and to accumulate the highest amount of water, which can affect the oxide formation on the Bipolar Plates (BPPs) and the Interfacial contact resistance (ICR)
It can be seen that the average ICR value obtained from three measuring points in situ is in the same range as the ICR value measured ex situ after fuel cell operation
Summary
Proton exchange membrane fuel cells (PEMFCs) convert chemical energy to electrical energy, and are predicted to play an important role in the future sustainable society.[1]. There are several studies described in the literature where interfacial contact resistance of stainless steel has been measured ex situ.[3,19,20,21,22] Lee and Lim[19] and Wang et al.[3] used a configuration which estimated the ICR by sandwiching a stainless steel plate between two carbon fiber papers (GDLs) in contact with copper plates in an outer structure. Lee and Lim[19] coated the stainless steel with a polymer-based coating containing various amounts of carbon black filler They measured ICR values between 25 m cm[2] and 850 m cm[2], where high carbon black content resulted in the lowest ICR values. Wang et al.[20] performed ICR measurements on both coated and non-coated stainless steel and reported an ICR of 66.4 m cm[2] at a compaction pressure of 274.4 N cm−2. Ex situ measurements of ICR between the bipolar plate and other components in the fuel cell have been thoroughly explored in the literature.[3,9,16,19,20,21,23,24,25,26,27,28,29,30,31,32] The literature describes various models for estimation of ICR in operating fuel cells.[32,33,34,35,36,37,38,39] Even though several attempts have been made to estimate the ICR inside an operating
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