Water crystallization inside fuel cell membranes probed by X-ray scattering

Mendil‐Jakani, Hakima; Davies, Richard J.; Dubard, Emilie; Guillermo, Armel; Gebel, Gérard

doi:10.1016/j.memsci.2010.11.059

Cited by 26 publications

(31 citation statements)

References 35 publications

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“…Confinement effect was proposed in several studies to explain the membrane behaviour [11,12,25,40]. We therefore compared the freezing point depression that would be given by a pure confinement effect, i.e.…”

Section: Confinement Versus Solution Effectmentioning

confidence: 99%

Water in a polymeric electrolyte membrane: Sorption/desorption and freezing phenomena

Plazanet

Sacchetti

Petrillo

et al. 2014

Journal of Membrane Science

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Section: Confinement Versus Solution Effectmentioning

confidence: 99%

Water in a polymeric electrolyte membrane: Sorption/desorption and freezing phenomena

Plazanet

Sacchetti

Petrillo

et al. 2014

Journal of Membrane Science

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“…Some studies based on differential scanning calorimetry (DSC) [21][22][23] conclude that part of the water in the membrane is freezable, while other studies using X-ray scattering contradict these findings. 24,25 Besides product water which is diffusing back into the membrane, water is present in the electrode. Concerning the aggregate state of water inside the electrode, contradictory findings have been published.…”

mentioning

confidence: 99%

When Size Matters: Active Area Dependence of PEFC Cold Start Capability

Biesdorf

Stahl

Siegwart

et al. 2015

J. Electrochem. Soc.

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Understanding the freezing mechanism of liquid water within polymer electrolyte fuel cells (PEFC) is crucial for its commercialization for mass market. Although various publications investigated the cold start capability of PEFCs, contradictory behaviors during cold starts at freezing temperatures have been published in literature. Interestingly, differences can be mainly identified between large and small size fuel cells: the latter have a significantly higher cold start capability than large size fuel cells. In order to understand the influence of different active areas, we present measurements of cold starts performed with cells sizes of 1 and 50 cm2 using the same materials, including a large count of experiments (>200) on the 1 cm2 cells to perform statistical analysis. The cold start capability is strongly reduced with an increasing size of the active area, and the operating times changes from stochastic values for small cells to reproducible values for large cells. Both effects can be explained by the higher probability of the aggregate state transition from super-cooled water to ice in large cells. Consequently this paper highlights the implications of downscaling PEFCs to draw conclusions for technical relevant cold-starts.

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“…To measure the membrane water content, the relation between the number of water molecules and SO 3 end groups, denoted by l, is introduced. These results were contradicted by another group reporting that ice formation in the membrane could only be observed at very high swelling states such as l = 50 [10]. Up to l = 14 of non-freezable water was reported [8], which maintains ionic conductivity even at temperatures far below 0°C.…”

Section: Introductionmentioning

confidence: 79%

“…Thompson et al proposed that the remaining free water can be frozen [9]. These results were contradicted by another group reporting that ice formation in the membrane could only be observed at very high swelling states such as l = 50 [10]. During a cold start, water uptake by the membrane is desirable as it prevents a part of residual or product water from freezing.…”

Section: Introductionmentioning

confidence: 97%

An Investigation of PEFC Sub‐Zero Startup: Influence of Initial Conditions and Residual Water

et al. 2017

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Isothermal cold starts of polymer electrolyte fuel cells were performed at sub‐zero temperatures and analyzed by means of neutron radiography in order to unravel the relation between the preconditioning of the cell and the cold start capability. It was found out that the initial humidification state of the membrane (determined by its resistance) has a clear correlation with the duration of the initial phase of the cold start, but not with the total duration of startup until cell failure. In the experimental setup the impact of realistic and commercial sealing solutions was taken into account by adding an edge channel. The impact of water accumulations in this region on the cold start capability was assessed. Liquid water located in the outer perimeter of a cell could be directly verified to freeze during cell cool down by a novel dual spectrum neutron radiography method. The amount of water accumulated in the outer cell perimeter showed some correlation with the total duration of the cold start. It was found out that residual water located in the edge channel can initiate freezing of a substantial part of the active area nearby.

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Water crystallization inside fuel cell membranes probed by X-ray scattering

Cited by 26 publications

References 35 publications

Water in a polymeric electrolyte membrane: Sorption/desorption and freezing phenomena

Water in a polymeric electrolyte membrane: Sorption/desorption and freezing phenomena

When Size Matters: Active Area Dependence of PEFC Cold Start Capability

An Investigation of PEFC Sub‐Zero Startup: Influence of Initial Conditions and Residual Water

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