Phase-change-related degradation of catalyst layers in proton-exchange-membrane fuel cells

Hwang, Gisuk; Kim, Hyoungchul; Lujan, Roger; Spernjak, Dusan; Borup, Rodney L.; Kaviany, Massoud; Kim, Moo Hwan; Weber, Adam Z.

doi:10.1016/j.electacta.2013.02.017

Cited by 37 publications

(25 citation statements)

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“…More and more experimental studies [11][12][13]42,44,[48][49][50]55,[96][97][98][99][100][101][102][103][104][105][106][107][108][109][110] have been performed simultaneously with numerical simulations to study the cell structure parameters and working conditions. Thompson et al [11] launched the research of the impact of F/T cycle on MEA, and the results showed that for membranes with water contents above λ = 8, the calorimetry and conductivity curves merged at low temperature, suggesting the formation of a common acid hydrate with similar network connectivity.…”

Section: Experimental Work On Cold Start Of Pemfcmentioning

confidence: 99%

“…Santamaria et al [104] studied cold start with different types of flow-field (parallel and interdigitated flow-field). Hwang et al [102] investigated the degradation of CLs associated with phase change in PEMFCs. Ko et al [89,103] studied the impacts of metallic bipolar plates and dual-function MPL to improve the cold-start capability of PEMFCs.…”

Section: Experimental Work On Cold Start Of Pemfcmentioning

confidence: 99%

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A Review on Cold Start of Proton Exchange Membrane Fuel Cells

et al. 2014

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Successful and rapid startup of proton exchange membrane fuel cells (PEMFCs) at subfreezing temperatures (also called cold start) is of great importance for their commercialization in automotive and portable devices. In order to maintain good proton conductivity, the water content in the membrane must be kept at a certain level to ensure that the membrane remains fully hydrated. However, the water in the pores of the catalyst layer (CL), gas diffusion layer (GDL) and the membrane may freeze once the cell temperature decreases below the freezing point (T f ). Thus, methods which could enable the fuel cell startup without or with slight performance degradation at subfreezing temperature need to be studied. This paper presents an extensive review on cold start of PEMFCs, including the state and phase changes of water in PEMFCs, impacts of water freezing on PEMFCs, numerical and experimental studies on PEMFCs, and cold start strategies. The impacts on each component of the fuel cell are discussed in detail. Related numerical and experimental work is also discussed. It should be mentioned that the cold start strategies, especially the enumerated patents, are of great reference value on the practical cold start process. OPEN ACCESSEnergies 2014, 7 3180

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Section: Experimental Work On Cold Start Of Pemfcmentioning

confidence: 99%

Section: Experimental Work On Cold Start Of Pemfcmentioning

confidence: 99%

A Review on Cold Start of Proton Exchange Membrane Fuel Cells

et al. 2014

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“…Numeric values are summarized in Table I. The PEM resistances demonstrate type dependence with Nafion NR-212 and HP having values of 0.303 ± 0.015 and 0.185 ± 0.005 cm 2 , respectively. The Sprayed MEAs had the lowest R H + for similar catalyst loadings, suggesting a more optimized CL structure.…”

Section: Resultsmentioning

confidence: 99%

The Effect of Material Properties on the Subzero Water Storage Capacity of Cathode Catalyst Layers for Proton Exchange Membrane Fuel Cells

Pistono¹,

Rice²

2017

J. Electrochem. Soc.

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Proton Exchange Membrane Fuel Cell cold start performance and durability from subzero conditions are dependent upon the cathode catalyst layer (CL) structure and interfacial binding to the membrane. The CL constituents and fabrication methodology impact the amount and location of freezing point depressed water available for proton conduction at subzero temperatures, water storage capacity and mechanical stability. Two common types of CL fabrication methods were studied to compare and contrast the nominal operational performance (80 • C polarization curves) and water storage capacity at −10 • C, −20 • C, and −30 • C; Decal Transfer versus Direct Spray. The cathode platinum on carbon CL constituents were also varied; ionomer-to-carbon support loadings (20wt% and 30wt%) and ionomer equivalent weight (830EW, 1000EW, and 1100EW). The different cathode CLs were assessed for resistance to proton conduction (R H + ) and electrochemical surface area (ECSA). The Sprayed cathode CL had the least R H + and highest ECSA, while decreasing the EW negatively impacted the electronic continuity of the CL. The baseline configuration (1100EW 30wt%) nominal operational iR-free voltages at 500 mA cm −2 were 50 mV higher for the Spray method. Subzero isothermal water fill tests (WFTs) at −10 mA cm −2 measured water storage capacity at freeze-out; Decal transfer was 2-2.5x higher than Spray CLs.

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“…During the operational lifetime of a PEFC, significant changes to material properties in each of these layers can occur as a result of the significant stresses associated with operational swings of temperature, RH, and voltage. These changes can be detrimental to performance and lifetime; thus, it is imperative that a comprehensive understanding of the degradation mechanisms and their impact on PEFC material properties is achieved; then, suitable mitigation strategies can be implemented.Previously, imaging of PEFC component degradation, particularly the cathode catalyst layer, which is vulnerable to damage during operational cycles, has primarily been limited to ex situ imaging, as well as, qualitative morphological changes [ 5,6]. Recent research by our group employing a Zeiss Versa 520 XCT system with a custom device holder design has enabled the 4D in-situ visualization of the full MEA during degradation cycles [ 3,4].…”

mentioning

confidence: 99%

“…Previously, imaging of PEFC component degradation, particularly the cathode catalyst layer, which is vulnerable to damage during operational cycles, has primarily been limited to ex situ imaging, as well as, qualitative morphological changes [ 5,6]. Recent research by our group employing a Zeiss Versa 520 XCT system with a custom device holder design has enabled the 4D in-situ visualization of the full MEA during degradation cycles [ 3,4].…”

mentioning

confidence: 99%

Quantification of Material Property Changes During Electrode Degradation in Polymer Electrolyte Fuel Cells Using X-ray Computed Tomography

et al. 2017

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Recent developments in lab-based X-ray Computed Tomography (XCT) systems has provided the ability to obtain non-destructive 3-dimensional imaging in numerous research fields, such as geology, materials science, and biomedical imaging [ 1]. A unique and prevalent application of this technique is to acquire a set of topographies at different experimental stages to assess any dynamic changes and obtain 4-dimensional imaging of a system under study [ 2]. This methodology is well suited for the study of polymer electrolyte fuel cell systems where detailed imaging of the membrane electrode assembly (MEA) can be obtained while it is still assembled in its operational housing [ 3].Polymer electrolyte fuel cells (PEFCs) are comprised of layered structures, each with their own material properties, providing the functionality to convert hydrogen and air into usable electrical power, heat, and water. These layers can be separated into: flow fields, gas diffusion layers, cathode/anode catalyst layers, and membrane. XCT imaging relies directly on the physical properties of materials, such as density and elemental composition, to provide absorption contrast within an imaging field-of-view, which allows for the clear identification of the various materials within PEFCs [ 4]. During the operational lifetime of a PEFC, significant changes to material properties in each of these layers can occur as a result of the significant stresses associated with operational swings of temperature, RH, and voltage. These changes can be detrimental to performance and lifetime; thus, it is imperative that a comprehensive understanding of the degradation mechanisms and their impact on PEFC material properties is achieved; then, suitable mitigation strategies can be implemented.Previously, imaging of PEFC component degradation, particularly the cathode catalyst layer, which is vulnerable to damage during operational cycles, has primarily been limited to ex situ imaging, as well as, qualitative morphological changes [ 5,6]. Recent research by our group employing a Zeiss Versa 520 XCT system with a custom device holder design has enabled the 4D in-situ visualization of the full MEA during degradation cycles [ 3,4]. Additional information that can still be gained relates to other fundamental material properties such as density and composition change, and visualizing these changes during 4D imaging.In this work we present a novel approach using a 4D in-situ lab-based XCT imaging technique to obtain quantitative material changes that occur during an accelerated stress test of a cathode catalyst layer within an operational PEFC. Post data acquisition with image processing yields results of material property changes such as: density, platinum and ionomer loadings, crack formation and propagation, and thickness changes; highlighting the capabilities of this novel approach for lab-based XCT systems. Figure 1 shows the resultant structural changes following accelerated degradation cycling of a cathode catalyst layer where crack propagation and crack formatio...

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Phase-change-related degradation of catalyst layers in proton-exchange-membrane fuel cells

Cited by 37 publications

References 37 publications

A Review on Cold Start of Proton Exchange Membrane Fuel Cells

A Review on Cold Start of Proton Exchange Membrane Fuel Cells

The Effect of Material Properties on the Subzero Water Storage Capacity of Cathode Catalyst Layers for Proton Exchange Membrane Fuel Cells

Quantification of Material Property Changes During Electrode Degradation in Polymer Electrolyte Fuel Cells Using X-ray Computed Tomography

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