Creep properties of catalyst coated membranes for polymer electrolyte fuel cells

Alavijeh, Alireza Sadeghi; Khorasany, Ramin M.H.; Habisch, Aronne; Wang, G. Gary; Kjeang, Erik

doi:10.1016/j.jpowsour.2015.03.082

Cited by 69 publications

(26 citation statements)

References 28 publications

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“…Due to the loss of CCM integrity in these regions, it is likely that the local membrane stresses are exacerbated in the absence of the reinforcing effect otherwise known to occur. 14,16 Qualitatively, larger and more frequent microstructural damage features were detected in the cross section of AMST-2 when compared to AMST-1, indicating that the AMST-2 MEAs were subjected to harsher conditions for mechanical membrane degradation.…”

Section: Resultsmentioning

confidence: 99%

“…The time dependent mechanical response of the CCM to variations in temperature, RH, and tensile stress was recently assessed by Sadeghi et al 16 through tensile creep and recovery tests. Both studies revealed significant reinforcement obtained when the membrane is coated with catalyst layers.…”

mentioning

confidence: 99%

“…Mechanical properties of CCM composites were comprehensively investigated by our group and compared to those of the corresponding PFSA membranes. [14][15][16][17] By conducting tensile stress-strain and dehydration tests under a wide range of temperature and RH conditions, Goulet et al…”

mentioning

confidence: 99%

“…13 The humidity cycles were conducted using relatively long humidity steps of 30 min duration with small amplitudes from 30% to 80% and from 80% to 120% RH, 13 hence mainly introducing creep stresses to the membrane analogous to the creep-recovery cycles reported in. 16 The decay in mechanical properties of CCMs subjected to combined chemical and mechanical degradation was systematically examined by our group 43 using tensile and expansion experiments in order to capture both time-independent and time-dependent mechanical responses of the CCM. In this case, the supplementary expansion experiments were found to provide a novel, insightful bridge between the in-situ swelling and contraction due to hygrothermal swings and the ex-situ measured tensile properties.…”

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confidence: 99%

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Microstructural and Mechanical Characterization of Catalyst Coated Membranes Subjected to In Situ Hygrothermal Fatigue

Alavijeh

Khorasany

Nunn

et al. 2015

J. Electrochem. Soc.

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Catalyst coated membranes (CCMs) in polymer electrolyte fuel cells are subjected to mechanical stresses in the form of fatigue and creep that deteriorate the durability and lifetime of the cells. The present article aims to determine the effect of in-situ hygrothermal fatigue on the microstructure and mechanical properties of the CCM. The fatigue process is systematically explored by the application of two custom-developed accelerated mechanical stress test (AMST) experiments with periodic extraction of partially degraded CCMs. Cross sectional and top surface scanning electron microscope (SEM) images of the end-of-test CCMs reveal the formation of mechanically induced cracks and delamination due to cyclic tensile and compressive fatigue stress. Tensile and expansion tests are conducted at different stages of degradation to evaluate the evolution in the mechanical and hygrothermal properties of the CCM. The tensile test results indicate gradual reductions in final strain, ultimate tensile strength, and fracture toughness with increasing number of fatigue cycles. The decay in tensile properties is attributed to the microstructural damage and micro-cracks formed during the AMST. Moreover, it is shown that the hygrothermal expansion of the CCM is more sensitive to conditioning than mechanical degradation. Polymer electrolyte fuel cells (PEFCs) are a prime candidate to replace gasoline and diesel internal combustion engines for transportation applications due to their environmental benefits combined with rapid start-up, high efficiency, and high power density at relatively low operating temperature.1 The commercialization of PEFCs is dependent on the development of membrane electrode assemblies (MEA) capable of meeting the automotive industry durability targets.2 However, the current PEFC technology is facing insufficient longevity, mainly because of the deterioration of the proton exchange membrane (PEM) component.1 Hence, an essential step to accomplish the commercialization requirements for PEFCs is to enhance the membrane durability and lifetime. Among various types of membranes utilized in PEFCs, perfluorosulfonic acid (PFSA) ionomer membranes (e.g., Nafion from DuPont) are the most widely used materials due to the superior chemical stability attributed to the chemically inert C-F bonds of the polytetrafluoroethylene (PTFE) base structure. 3Chemical and mechanical degradation mechanisms are recognized as the principal root causes for lifetime limiting failures of PFSA ionomer membranes in fuel cells. Understanding of the degradation mechanisms, their interactions, and the corresponding failure modes could provide valuable insight toward decelerating the rate of the membrane degradation and thereby extend the lifetime.2 Chemical degradation is caused by the attack of radical species in the form of hydroxyl (•OH) and hydroperoxyl (•OOH) radicals generated through decomposition of hydrogen peroxide (H 2 O 2 ) by metal contaminants.2,4,5 Hydroxyl radicals also form as a by-product of the electrochemical reaction bet...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Microstructural and Mechanical Characterization of Catalyst Coated Membranes Subjected to In Situ Hygrothermal Fatigue

Alavijeh

Khorasany

Nunn

et al. 2015

J. Electrochem. Soc.

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“…Prolonged membrane exposure to these stresses causes mechanical rupture via fatigue (cyclic stress) and/or creep (constant stress) phenomena. 12,13,20,23,33 Moreover, mechanical properties of the membrane deteriorate during chemical degradation;…”

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confidence: 99%

3D Failure Analysis of Pure Mechanical and Pure Chemical Degradation in Fuel Cell Membranes

Singh

Orfino

Dutta

et al. 2017

J. Electrochem. Soc.

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Lifetime-limiting failure of fuel cell membranes is generally attributed to their chemical and/or mechanical degradation. Although both of these degradation modes occur concurrently during operational duty cycles, their uncoupled investigations can provide useful insights into their individual characteristics and consequential impacts on the overall membrane failure. X-ray computed tomography is emerging as an advantageous tool for fuel cell failure analysis due to its non-destructive and non-invasive 3D imaging capabilities at ambient conditions. In the present work, post-mortem failure analysis of pure mechanical and pure chemical membrane degradation modes is performed three-dimensionally using this technique. A uniquely comprehensive analysis afforded by this technique reveals that membrane failure is almost exclusively characterized by crack formations during mechanical degradation and by severe thinning accompanied by electrode shorting and pinhole formation during chemical degradation, respectively. Catalyst layer cracks, particularly on the cathode side, are found to interact strongly with mechanically induced membrane cracks. The conjoint effect of chemical and mechanical stressors is established as a necessary requirement for: (i) exclusive membrane crack development independent of catalyst layer cracks; and (ii) crack branching during membrane crack propagation. Overall, the membrane failure analysis improves its reliability and quantitative character with the adoption of 3D imaging. The transportation sector is a significant contributor to global greenhouse gas emissions and with ever-growing concerns around the global warming effect, research and development of novel clean energy based automotive solutions is being pursued worldwide. Hydrogen fuel cells have thus far emerged as a promising alternative to fossil fuel based internal combustion engines due to their clean, noisefree, and efficient operation.1 Polymer electrolyte membrane (PEM) fuel cells 2 are widely used in fuel cell electric vehicles (FCEVs) and supply electrical energy from the electrochemical conversion of hydrogen and oxygen (usually supplied as air) into water. In automotive applications, the fluctuating operating conditions due to vehicle dynamics, variations in loads and environmental conditions, startups and shutdowns, fuel starvation, contamination, and freeze-thaw cycles pose significant durability challenges for the PEM fuel cells. 3Understanding the specific durability problems and developing suitable solutions remains a key research focus in automotive PEM fuel cell technology research and is critical to the long-term and large-scale commercial adoption of this technology. Given the complex interplay of multiple physical phenomena that are simultaneously active in an operating PEM fuel cell, various deleterious factors affecting PEM fuel cell components can collectively lead to a gradual performance loss and eventual failure.In PEM fuel cells, the electrodes are separated by a polymeric membrane which allows selective tran...

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Mechanical responses in the length direction and thickness direction of quaternary 1,4‐diazabicyclo‐[2.2.2]‐octane polysulfone alkaline anion‐exchange fuel‐cell membranes

Zhang

Tian

et al. 2019

J of Applied Polymer Sci

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A quaternary 1,4-diazabicyclo-[2.2.2]-octane polysulfone (QDPSU) alkaline anion-exchange fuel-cell membrane was synthesized. Nanoindentation and uniaxial tension methods were used to test the mechanical properties of this membrane in both the thickness direction and length direction at 26 C and 40% relative humidity. We found that the QDPSU membrane exhibited remarkable viscoelastic properties with significant loading rate-dependent behavior and time-dependent behavior (creep-relaxation). The value of compression creep rates and compression relaxation rates of the QDPSU membrane were measured to be about 0.2 by a spherical indenter and changed very little with different holding loads. Compared with Nafion, a most widely used fuel-cell membrane, the QDPSU alkaline anion-exchange membrane showed a better creep resistance. During the nanoindentation fatigue test, the variation of depths with the indentation cycles were divided into a rising primary region, a steady-state secondary region, and a continuous declining region. This was different from the uniaxial tension fatigue test. The cross-scale and cross-direction mechanical study from this work will help provide new evidence for bridging the gap between nanoindentation and uniaxial tensile testing.

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Creep properties of catalyst coated membranes for polymer electrolyte fuel cells

Cited by 69 publications

References 28 publications

Microstructural and Mechanical Characterization of Catalyst Coated Membranes Subjected to In Situ Hygrothermal Fatigue

Microstructural and Mechanical Characterization of Catalyst Coated Membranes Subjected to In Situ Hygrothermal Fatigue

3D Failure Analysis of Pure Mechanical and Pure Chemical Degradation in Fuel Cell Membranes

Mechanical responses in the length direction and thickness direction of quaternary 1,4‐diazabicyclo‐[2.2.2]‐octane polysulfone alkaline anion‐exchange fuel‐cell membranes

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