Influence of humidification on deterioration of gas diffusivity in catalyst layer on polymer electrolyte fuel cell

Hiramitsu, Yusuke; Sato, Hitoshi; Hosomi, Hiroyuki; Aoki, Yasuhito; Harada, Takahiro; Sakiyama, Yoko; Nakagawa, Y.; Kobayashi, Kenji; Hori, Michio

doi:10.1016/j.jpowsour.2009.07.035

Cited by 33 publications

(18 citation statements)

References 37 publications

(44 reference statements)

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“…19 Humidification has also been demonstrated to have a significant impact on in situ component degradation. 20 Design changes that increase water retention may thus also increase performance losses caused by corrosive conditions. The cell water holdup and performance is also expected to change based on the extent of corrosion, since several of the factors that regulate water retention and removal are affected by corrosion: 1) Catalyst layer porosity is reduced as the carbon support is lost and the pore structure collapses.…”

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confidence: 99%

Effects of Cathode Corrosion on Through-Plane Water Transport in Proton Exchange Membrane Fuel Cells

Fairweather

Spernjak

Weber

et al. 2013

J. Electrochem. Soc.

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The corrosion of carbon in the cathodes of proton-exchange-membrane fuel cells leads to electrode collapse, reduced active catalyst area, and increased surface hydrophilicity. While these effects have been linked to performance degradation over cell lifetime, the role of corrosion in the evolving water balance has not been clear. In this study, neutron imaging was used to evaluate the through-plane water distribution within several cells over the course of accelerated stress testing using potential holds and square-wave cycling. A dramatic decrease in water retention was observed in each cell after the cathode was severely corroded. The increasing hydrophilic effect of carbon surface oxidation (quantified by ex situ X-ray photoelectron spectroscopy) was overwhelmed by the drying effect of increased internal heat generation. To evaluate this mechanism, the various observed electrode changes are included in a multiphase, non-isothermal one-dimensional cell model, and the simulated alterations to cell performance and water content are compared with those observed experimentally. Simulation results are consistent with the idea that collapse and compaction of the catalyst layer is the dominant limitation to cell performance and not the lower amounts of active Pt surface area, and that higher temperature gradients result in drying out of the cell.The corrosion of carbonaceous components in proton-exchangemembrane fuel cells (PEMFCs) is a concern for long-term durability. Carbon corrosion can cause performance losses through several mechanisms. 1 As carbon catalyst support is lost, catalyst activity is lost due to particle detachment, agglomeration and/or isolation. The pore space is collapsed, blocking transport pathways for oxygen to the active catalyst sites. Surfaces can be made more hydrophilic by roughening and addition of oxide surface groups, 2,3 thereby increasing the propensity of flooding. While the kinetics of carbon corrosion are usually slow at PEMFC operating temperatures and normal potentials, regional reversals and starvation lead to high local potentials and accelerated oxidation. 4,5 Moreover, carbon corrosion is catalyzed by contact with platinum in the electrodes. 6,7 Automotive applications of PEMFCs require an estimated 5500 h of operation including 38,500 startup/shutdown cycles. 8 Each of these cycles involves brief high potential excursions that can accelerate corrosion. 4,5 During operational periods, transient power demands and localized water blockage 9 can result in bulk or regional fuel starvation, 10-12 also leading to more corrosive conditions. Altogether, this is a demanding environment for carbonaceous components, and requires a combination of corrosion-resistant materials (typically graphitized carbons) 13 and careful system management strategies 14 to achieve acceptable durability. To evaluate rapidly the suitability of different support materials for a PEMFC cathode, accelerated stress tests (ASTs) have been developed which greatly accelerate corrosion. These ASTs commonly raise the...

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confidence: 99%

Effects of Cathode Corrosion on Through-Plane Water Transport in Proton Exchange Membrane Fuel Cells

Fairweather

Spernjak

Weber

et al. 2013

J. Electrochem. Soc.

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“…As electrochemical energy converters, these fuel cells enable the direct and efficient conversion of hydrogen energy into power for stationary, portable and automobile applications. [8][9][10] Thus, water management has been the main focus of study for numerous groups in recent years. 1,2 Water management represents one of the main challenges in the design and operation of PEMFCs.…”

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confidence: 99%

Oscillation of PEFC under Low Cathode Humidification: Effect of Gravitation and Bipolar Plate Design

Sánchez

Ortiz

Friedrich

2013

J. Electrochem. Soc.

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Oscillatory fluctuations of a single proton exchange membrane fuel cell appear upon operation with a dry cathode air supply and a fully humidified anode stream. Periodic transitions between a low-and high-current operation point of the oscillating state due to the balance of drying and wetting processes in combination with water transport have been observed previously; however, several new aspects have been investigated in the present study, providing insight into the initiation processes. Oscillations are present under both galvanostatic and potentiostatic conditions, and it is demonstrated that the transitions involve local membrane drying through the comparison of impedance data with current density distributions. The oscillations are caused by periodic flow type changes from one-to two-phase flow in the anodic channels of the flow field. It has been observed that cell orientation with respect to Earth's gravity field affects the liquid water distribution in the anodic flow channels and, thus, also affects the oscillatory behavior of the cell performance. When comparing cell performance oscillations with a five-channel serpentine flow field to a cell with a one-channel serpentine flow field, the oscillating performance behavior is observed to also be affected by the gas velocity within an anodic flow channel.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 157.182.150.22 Downloaded on 2015-06-22 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 157.182.150.22 Downloaded on 2015-06-22 to IP F640 Journal of The Electrochemical Society, 160 (6) F636-F644 (2013) ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 157.182.150.22 Downloaded on 2015-06-22 to IP

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“…This indicates that intercalated water could have a similar effect on the d-spacing. Hiramitsu et al [36] observed a peak around 1750 to 1850 cm -1 related to C=O vibrations [29].…”

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confidence: 98%

Reduced Graphene Oxide for Li-Air Batteries: The Effect of Oxidation Time and Reduction Conditions for Graphene Oxide

Storm,

Overgaard,

Younesi

et al. 2013

Meet. Abstr.

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Influence of humidification on deterioration of gas diffusivity in catalyst layer on polymer electrolyte fuel cell

Cited by 33 publications

References 37 publications

Effects of Cathode Corrosion on Through-Plane Water Transport in Proton Exchange Membrane Fuel Cells

Effects of Cathode Corrosion on Through-Plane Water Transport in Proton Exchange Membrane Fuel Cells

Oscillation of PEFC under Low Cathode Humidification: Effect of Gravitation and Bipolar Plate Design

Reduced Graphene Oxide for Li-Air Batteries: The Effect of Oxidation Time and Reduction Conditions for Graphene Oxide

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