Modeling of Transient Platinum Degradation in a Low Pt-Loading PEFC under Current Cycling

Li, Yubai; Wang, C.Y.

doi:10.1149/2.0081704jes

Cited by 34 publications

(12 citation statements)

References 64 publications

(87 reference statements)

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“…Pt catalyst particles at specific locations are exposed to different local conditions (e.g. relative humidity (RH), liquid water content and gas composition (H 2 and O 2 gradients in the case of H 2 /air operation), thus the localized degradation behavior likely deviates [12][13][14][15] . So far, 1-D segmented cell design has shown some progress in delivering insights into electrocatalyst degradation from start-up and shut-down cycles, showing non-uniform ECSA loss between inlet and outlet regions [16,17] .…”

Section: Introductionmentioning

confidence: 99%

Mapping of Heterogeneous Catalyst Degradation in Polymer Electrolyte Fuel Cells

Cheng

Khedekar

Talarposhti

et al. 2020

Advanced Energy Materials

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Pt catalyst in polymer electrolyte fuel cells degrades heterogeneously as the catalyst particles are exposed to local variations throughout the catalyst layer during operation. State-of-the-art analytical techniques for studying degradation of Pt catalyst do not possess fine spatial resolution to elucidate such non-uniform degradation behavior at a large electrode level. A new methodology is developped to spatially resolve and quantify the heterogeneous Pt catalyst degradation over a large area (several cm 2 ) of aged MEAs based on synchrotron Xray micro-diffraction. PEFC single cells are aged using voltage cycling as an accelerated stress test and the degradation heterogeneity at a micrometer length scale is visualized by mapping Pt catalyst particle size after voltage cycling. We demonstrated in details that the Pt catalyst particle size growth is non-uniform and follows the flow field geometry. The Pt particle size growth is greater in the area under the flow field land, while it is minimal in the area under the flow field channel. Additional non-uniformity is observed with the Pt particle size increasing more rapidly at the gas outlet area of than the Pt particle size at the inlet area.

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Section: Introductionmentioning

confidence: 99%

Mapping of Heterogeneous Catalyst Degradation in Polymer Electrolyte Fuel Cells

Cheng

Khedekar

Talarposhti

et al. 2020

Advanced Energy Materials

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“…Nevertheless, the scaling factors are considered to have a negative effect on performance since the scaling modifications increase the complexity of the flow field and the pumping power. (5) The analyses, especially the scaling factors, show that the cell performance is significantly affected by the changes in the geometry of the baffles, therefore it is advisable to conduct the design of experiments and optimization for different operating conditions to determine the most appropriate geometry parameters for achieving the possible highest performance.…”

Section: Supplementary Materialsmentioning

confidence: 99%

“…Operation at high power densities is a limiting factor for PEM fuel cells due to the accumulation of significant quantities of liquid water inside the catalyst layers (CLs), gas diffusion layers (GDLs), and reactant channels, resulting in poor performance due to uneven spatial distribution of current density and the accompanying heat and mass transfer [4]. Operation with a significant amount of liquid water inside the cell during transient operating conditions, e.g., at starting and stopping or load cycling, results in higher degradation rates owing to the highly non-uniform heat and mass transfer over the active area [5]. Hence, mitigation strategies have been developed to reinforce oxygen transport to the CLs by minimizing the water blockage between the flow field and GDLs [6].…”

Section: Introductionmentioning

confidence: 99%

Combining Baffles and Secondary Porous Layers for Performance Enhancement of Proton Exchange Membrane Fuel Cells

et al. 2021

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A numerical study is conducted to compare the current most popular flow field configurations, porous, biporous, porous with baffles, Toyota 3D fine-mesh, and traditional rectangular flow field. Operation at high current densities is considered to elucidate the effect of the flow field designs on the overall heat transfer and liquid water removal. A comprehensive 3D, multiphase, nonisothermal computational fluid dynamics model is developed based on up-to-date heat and mass transfer sub-models, incorporating the complete formulation of the Forchheimer inertial effect and the permeability ratio of the biporous layers. The porous and baffled flow field improves the cell performance by minimizing mass transport losses, enhancing the water removal from the diffusion layers. The baffled flow field is chosen for optimization owing to the simple design and low manufacturing cost. A total of 49 configurations were mutually compared in the design of experiments to show the quantitative effect of each parameter on the performance of the baffled flow field. The results elucidate the significant influence of small geometry modifications on the overall heat and mass transfer. The results of different cases have shown that water saturation can be decreased by up to 33.59% and maximal temperature by 7.91 °C when compared to the reference case which is already characterized by very high performance. The most influencing geometry parameters of the baffles on the cell performance are revealed. The best case of the 49 studied cases is further optimized by introducing a linear scaling factor. Additional geometry modifications demonstrate that the gain in performance can be increased, but at a cost of higher pressure drop and increased design complexity. The conclusions of this work aids in the development of compact and high-performance proton exchange membrane fuel cell stacks.

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“…where ε = 0.70 is the porosity of the GDL [122], λ GDL = 0.5 W m −1 К −1 is the heat conductivity of carbon [8], and λ H2 = 0.183 W m −1 К −1 and λ air = 0.0276 W m −1 К −1 are the heat conductivities of H 2 and air. Additional parameters and assumptions were used according to the standard practices in PEMFC modeling [123,124].…”

Section: Coupling Convection and Electrochemistrymentioning

confidence: 99%

Effect of the corrugated bipolar plate design on the self‐humidification of a high power density PEMFC stack for UAVs

et al. 2021

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Open-cathode PEMFCs for unmanned aerial vehicles operate at a near-ambient temperature, which requires high super-stoichiometric air flow rates to remove heat. This, in turn, makes the stack vulnerable to drying out. Using a combination of experimental measurements with a 1.2 kW stack and 3D multiphysics modelling, we show that the design of the corrugated metal bipolar plate with a height above the commonly used 1.05 mm and with cathode cooling channels wider than air-suppling channels allows for a more efficient heat removal at lower air flow rates, thus assuring a wider range of operating parameters, while maintaining adequate hydration. The self-humidifying stack attains 1000 W kg −1 power, and the full system with a nominal runtime of 4 h attains specific energy of 700 Wh kg −1 .

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Modeling of Transient Platinum Degradation in a Low Pt-Loading PEFC under Current Cycling

Cited by 34 publications

References 64 publications

Mapping of Heterogeneous Catalyst Degradation in Polymer Electrolyte Fuel Cells

Mapping of Heterogeneous Catalyst Degradation in Polymer Electrolyte Fuel Cells

Combining Baffles and Secondary Porous Layers for Performance Enhancement of Proton Exchange Membrane Fuel Cells

Effect of the corrugated bipolar plate design on the self‐humidification of a high power density PEMFC stack for UAVs

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