Effects of ionomer content and oxygen permeation of the catalyst layer on proton exchange membrane fuel cell cold start-up

Hiramitsu, Yusuke; Mitsuzawa, N.; Okada, Kazuko; Hori, Michio

doi:10.1016/j.jpowsour.2009.08.016

Cited by 42 publications

(16 citation statements)

References 30 publications

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“…Following a constant current density of 20 mA/cm 2 , cell voltage remains constant until failure (i.e., when cell voltage rapidly decreases to 0 mV) as a result of ice formation within the cathode. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]35 We define the cell-failure time, t f ail , as the time elapsed between the onset of constant cell voltage and 0 mV. We do not include the 30-min stabilization period when determining measured t f ail .…”

Section: Resultsmentioning

confidence: 99%

“…Solid lines correspond to ice-crystallization kinetics (i.e., Eqs. [4][5][6][7][8] for two cCL carbon-support materials with considerably different icecrystallization kinetics: Vulcan XC72 and BP460. The dashed line is predicted using a traditional thermodynamic-based approach with k f = 0.25 kg/m 3 s. 18 In all cases, t f ail decreases substantially with increasing T , in good agreement with experiment.…”

Section: Isothermal Pemfc Cold-start Modelmentioning

confidence: 99%

“…To date, experiments predominately focus on characterizing overall low-temperature cell performance. [1][2][3][4][5][6][7] In recent years, however, in-situ visualization and detection of ice formation within PEMFC porous media has progressed. [7][8][9][10][11][12][13][14] Visualization methods include neutron radiography, 8,9 environmental scanning electron microscopy, 10 visible imaging, [11][12][13] and latent-heat detection with infrared thermography.…”

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confidence: 99%

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Ice-Crystallization Kinetics in the Catalyst Layer of a Proton-Exchange-Membrane Fuel Cell

Dursch

Trigub

Lujan

et al. 2013

J. Electrochem. Soc.

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Nucleation and growth of ice in the catalyst layer of a proton-exchange-membrane fuel cell (PEMFC) are investigated using isothermal differential scanning calorimetry and isothermal galvanostatic cold-starts. Isothermal ice-crystallization rates and icenucleation rates are obtained from heat-flow and induction-time measurements at temperatures between 240 and 273 K for four commercial carbon-support materials with varying ionomer fraction and platinum loading. Measured induction times follow expected trends from classical nucleation theory and reveal that the carbon-support material and ionomer fraction strongly impact the onset of ice crystallization. Conversely, dispersed platinum particles play little role in ice crystallization. Following our previous approach, a nonlinear ice-crystallization rate expression is obtained from Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory. A validated rate expression is now available for predicting ice crystallization within water-saturated catalyst layers. Using a simplified PEMFC isothermal cold-start continuum model, we compare cell-failure time predicted using the newly obtained rate expression to that predicted using a traditional thermodynamic-based approach. From this comparison, we identify conditions under which including ice-crystallization kinetics is critical and elucidate the impact of freezing kinetics on low-temperature PEMFC operation. The numerical model illustrates that cell-failure time increases with increasing temperature due to a longer required time for ice nucleation. Hence, ice-crystallization kinetics is critical when induction times are long (i.e., in the "nucleation-limited" regime for T > 263 K). Cell-failure times predicted using ice-freezing kinetics are in good agreement with the isothermal cold-starts, which also exhibit long and distributed cell-failure times for T > 263 K. These findings demonstrate a significant departure from cell-failure times predicted using the thermodynamic-based approach.Proton-exchange-membrane fuel cells (PEMFCs) show promise in automotive applications because of their high efficiency, high power density, and potentially low emissions. To be successful in automotive applications, PEMFCs must permit rapid startup with minimal energy from sub-freezing temperatures, known as cold-start. In a PEMFC, reduction of oxygen to water occurs in the cathode catalyst layer (cCL). Under subfreezing conditions, water solidifies and hinders access of gaseous oxygen to the catalytic sites in the cCL, severely inhibiting cell performance and potentially causing cell failure. 1-3 Elucidation of the mechanisms and kinetics of ice formation within the cCL is, therefore, critical to successful cell startup and high performance at low temperatures.Because of degradation and cell failure under subfreezing conditions, much attention has been given to understanding cold-start fundamentals. To date, experiments predominately focus on characterizing overall low-temperature cell performance.

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Section: Resultsmentioning

confidence: 99%

Section: Isothermal Pemfc Cold-start Modelmentioning

confidence: 99%

mentioning

confidence: 99%

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Ice-Crystallization Kinetics in the Catalyst Layer of a Proton-Exchange-Membrane Fuel Cell

Dursch

Trigub

Lujan

et al. 2013

J. Electrochem. Soc.

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“…11 It is impossible to directly compare results by Hiramitsu et al and Mishler et al on ionomer content as their fabrication and testing protocols differ drastically, however the general trend observed was that higher ionomer-to-carbon ratios increased the water storage capacity. 12,13 Further, Mishler et al demonstrated that the water storage capacity does not linearly scale with cathode CL thickness, attributing this phenomena to spatial variations of the reaction. 13 Several WFT-based models have evolved with a rudimentary predictive capability to extend the water fill capacity.…”

Section: 10mentioning

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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“…Газопроницаемость КС топливной ячейки МЭБ обсуждалась в работе [7] с точки зрения интенсивности проницаемости кислорода. Было показано, что тип используемого иономера в КС влияет на холодный запуск топливных элементов с протонпроводящей мембраной [8].…”

Section: рис 1 принципиальная схема процессов массопереноса в мембрunclassified

Mathematical Methodology and Software Package for Experiments to Study the Transient Hydrogen Permeation in Membranes Used in Electrolysers and Hydrogen Fuel Cell

Bekman¹,

Bessarabov²,

Buntseva³

2016

Alʹtern. ènerg. èkol.

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В рамках создания методологии управления процессами проницаемости функциональных материалов рассмотрен математический аппарат диффузии через пластину при граничных условиях 1-го и 2-го рода и предложены способы оценки параметров диффузии методами особых точек, функциональных масштабов и статистических моментов. Разработан комплекс компьютерных программ HPRON, обеспечивающий возможность математического моделирования, планирования, обработки и интерпретации результатов различных вариантов метода газопроницаемости. Полученные результаты использованы для оптимизации работы мембранного электродного блока автомобильного топливного элемента и электролизера с протонпроводящей перфторированной мембраной типа нафиона.

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Effects of ionomer content and oxygen permeation of the catalyst layer on proton exchange membrane fuel cell cold start-up

Cited by 42 publications

References 30 publications

Ice-Crystallization Kinetics in the Catalyst Layer of a Proton-Exchange-Membrane Fuel Cell

Ice-Crystallization Kinetics in the Catalyst Layer of a Proton-Exchange-Membrane Fuel Cell

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

Mathematical Methodology and Software Package for Experiments to Study the Transient Hydrogen Permeation in Membranes Used in Electrolysers and Hydrogen Fuel Cell

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