Analysis of a cathode catalyst layer model for a polymer electrolyte fuel cell

Berg, Peter; Novruzi, Arian; Promislow, Keith

doi:10.1016/j.ces.2006.01.033

Cited by 23 publications

(18 citation statements)

References 14 publications

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“…[51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68]92,93 To account for such an interface, the membrane water-uptake boundary condition is altered to include a mass-transfer coefficient instead of assuming an equilibrium isotherm directly N = k mt (a in − a out ) [40] where in and out refer to the water activities directly inside and outside of the membrane interface (which can be defined from FloryRehner equation in the polymer 94 and the relative humidity in the gas phase, respectively) and k mt is a mass-transfer coefficient that can be a function of local conditions (e.g., humidity, temperature, gas-velocity, etc.). 51,52,54,58,61,62,[64][65][66][67][68]92,93 This approach is the same as including a surface reaction (e.g., condensation) at the membrane interface, [95][96][97] and is not as often used in modeling as perhaps it should be. One caveat to the above is that it must be used in such a way that the activity is defined at at least one boundary of the membrane in order to avoid multiple solutions.…”

Section: Basic Governing Equationsmentioning

confidence: 99%

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

Weber

Borup

Darling³

et al. 2014

J. Electrochem. Soc.

496

394

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Polymer-electrolyte fuel cells are a promising energy-conversion technology. Over the last several decades significant progress has been made in increasing their performance and durability, of which continuum-level modeling of the transport processes has played an integral part. In this review, we examine the state-of-the-art modeling approaches, with a goal of elucidating the knowledge gaps and needs going forward in the field. In particular, the focus is on multiphase flow, especially in terms of understanding interactions at interfaces, and catalyst layers with a focus on the impacts of ionomer thin-films and multiscale phenomena. Overall, we highlight where there is consensus in terms of modeling approaches as well as opportunities for further improvement and clarification, including identification of several critical areas for future research. Fuel cells may become the energy-delivery devices of the 21 st century. Although there are many types of fuel cells, polymer-electrolyte fuel cells (PEFCs) are receiving the most attention for automotive and small stationary applications. In a PEFC, fuel and oxygen are combined electrochemically. If hydrogen is used as the fuel, it oxidizes at the anode releasing proton and electrons according toThe generated protons are transported across the membrane and the electrons across the external circuit. At the cathode catalyst layer, protons and electrons recombine with oxygen to generate waterAlthough the above electrode reactions are written in single step, multiple elementary reaction pathways are possible at each electrode. During the operation of a PEFC, many interrelated and complex phenomena occur. These processes include mass and heat transfer, electrochemical reactions, and ionic and electronic transport. * Electrochemical Society Active Member. z E-mail: azweber@lbl.govOver the last several decades significant progress has been made in increasing PEFC performance and durability. Such progress has been enabled by experiments and computation at multiple scales, with the bulk of the focus being on optimizing and discovering new materials for the membrane-electrode-assembly (MEA), composed of the proton-exchange membrane (PEM), catalyst layers, and diffusionmedia (DM) backing layers. In particular, continuum modeling has been invaluable in providing understanding and insight into processes and phenomena that cannot be resolved or uncoupled through experiments. While modeling of the transport and related phenomena has progressed greatly, there are still some critical areas that need attention. These areas include modeling the catalyst layer and multiphase phenomena in the PEFC porous media.While there have been various reviews over the years of PEFC modeling 1-7 and issues, [8][9][10][11][12][13][14] as well as numerous books and book chapters, there is a need to examine critically the field in terms of what has been done and what needs to be done. This review serves that purpose with a focus on transport modeling of PEFCs. This is not meant to be an exhaustive review...

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Section: Basic Governing Equationsmentioning

confidence: 99%

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

Weber

Borup

Darling³

et al. 2014

J. Electrochem. Soc.

496

394

View full text Add to dashboard Cite

show abstract

“…In fact, recent studies have clearly shown that treating the cathode CL as an interface with uniform properties leads to several erroneous conclusions, especially due to the impact of channel-rib effects that distribute the electrons, water, heat, and oxygen unevenly at the CL boundary. [115][116][117][118] While an embedded agglomerate model is now utilized in most models, there is still an effort towards including more microstructural details.…”

Section: Catalyst-layer Modelingmentioning

confidence: 99%

Modeling Water Management in Polymer-Electrolyte Fuel Cells

Weber

Balliet

Gunterman

et al. 2008

Modern Aspects of Electrochemistry

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“…The transition between the vapor and liquid water is described with the help of a phenomenological model proposed in Ref. [6] and conceptually analogous to the common evaporation-condensation model. The rate of change of concentration of liquid water and vapor is assumed to be proportional to the deviation of the actual hydration λ from the equilibrium hydration λ e given by (8).…”

Section: Anodic Catalyst Layermentioning

confidence: 99%

“…The novelty of our approach is in the description of the transport and phase transformation of water within the catalyst layers. As opposite to almost all previous studies (the only exception [6] is discussed below), we do not assume equilibrium between the pore vapor and membrane liquid water but rather consider them as different phases equilibrating at a finite rate. Let us introduce the phenomenon and discuss it in some details.…”

Section: Introductionmentioning

confidence: 99%

“…We use the approach of Ref. [6], where a simple phenomenological model of the process was proposed and analyzed for the case of a separate cathode catalyst layer. The rate of equilibration is defined as a constant τ −1 γ , where τ γ is the typical relaxation (equilibration) time, which primarily depends on the volume fraction of the ionomer in the catalyst layer and the area of the contact surface.…”

Section: Introductionmentioning

confidence: 99%

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A computational model of a PEM fuel cell with finite vapor absorption rate

Vorobev

Zikanov

Shamim

2007

Journal of Power Sources

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The paper presents a new computational model of non-steady operation of a PEM fuel cell. The model is based on the macroscopic hydrodynamic approach and assumptions of low humidity operation and one-dimensionality of transport processes. Its novelty and advantage in comparison with similar existing models is that it takes into account the finite-time equilibration between vapor and membrane-phase liquid water within the catalyst layers. The phenomenon is described using an additional parameter with the physical meaning of the typical reciprocal time of the equilibration. A computational parametric study is conducted to identify the effect of the finite-time equilibration on steady-state and transient operation of a PEM fuel cell.

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Analysis of a cathode catalyst layer model for a polymer electrolyte fuel cell

Cited by 23 publications

References 14 publications

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

Modeling Water Management in Polymer-Electrolyte Fuel Cells

A computational model of a PEM fuel cell with finite vapor absorption rate

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