Prediction of anisotropic transport in Nafion containing catalyst layers

Dorenbos, G.; Pomogaev, Vladimir A.; Takigawa, M.; Morohoshi, Kei

doi:10.1016/j.elecom.2009.11.004

Cited by 32 publications

(43 citation statements)

References 11 publications

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“…When for the backbone A beads the handbook solubility value for Teflon (d A = 12.7 MPa 0.5 ) would be adapted then d W = 26.8 MPa 0.5 is obtained [32].…”

Section: Dissipative Particle Dynamicsmentioning

confidence: 99%

“…In order to be able to make conversions to physical length scales, similar as in Refs. [30][31][32]43,44], each W bead represents 4 water molecules, i.e. N m = 4 and V = 0.12 nm 3 .…”

Section: Polymer Chain Architecturementioning

confidence: 99%

“…Other methods that have been invoked to generate equilibrium morphologies of hydrated Nafion of size O(10 4 nm 3 ) from random starting configurations are Coarse Grained MD (CGMD) [25,26], Bond Fluctuation Model (BFM) [27], Monte Carlo in combination with the Reference Interaction Site Model (MC/RISM) [28], self-consistent approaches [29] and the dissipative particle dynamics (DPD) simulation method [30][31][32][33][34][35][36]. Yamamoto and Hyodo [30] applied DPD and calculated for system size $2.3 Â 10 4 nm 3 Nafion1200 morphologies (1200 means the equivalent weight (EW) of 1200 g polymer per one mole of sulfonic sites).…”

Section: Introductionmentioning

confidence: 99%

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Morphology and diffusion within model membranes: Application of bond counting method to architectures with bimodal side chain length distributions

Dorenbos¹

2015

European Polymer Journal

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“…When for the backbone A beads the handbook solubility value for Teflon (d A = 12.7 MPa 0.5 ) would be adapted then d W = 26.8 MPa 0.5 is obtained [32].…”

Section: Dissipative Particle Dynamicsmentioning

confidence: 99%

“…In order to be able to make conversions to physical length scales, similar as in Refs. [30][31][32]43,44], each W bead represents 4 water molecules, i.e. N m = 4 and V = 0.12 nm 3 .…”

Section: Polymer Chain Architecturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Morphology and diffusion within model membranes: Application of bond counting method to architectures with bimodal side chain length distributions

Dorenbos¹

2015

European Polymer Journal

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“…For instance, using dissipative particle dynamics, conductivity in CL ionomer on a carbon support was shown to be anisotropic due to the layered structure in the electrolyte. 359 Since orientation of water domains in thin films are already observed to change with wetting interactions and substrate (using GISAXS), advances in experimental and simulation techniques must be taken advantage of to obtain more information on size-distribution and orientation of domains. Only by understanding the role of film thickness and substrate/film interactions in structure/functionality of thin-film ionomers on PEFC relevant substrates and conditions, can one develop tools to achieve optimum ionomer content, better Pt utilization or reduced Pt loading, and ultimately improved catalyst-layer performance.…”

Section: 142mentioning

confidence: 99%

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

Weber

Borup

Darling³

et al. 2014

J. Electrochem. Soc.

509

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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“…26 Borges used the same method to gain insight into the hydrophobicity of Nafion surface. 27,28 On the mesoscale level, Dorenbos et al simulated Nafion confined by carbon surfaces at various hydrophobicities, which were controlled by the solubility parameter, 29 revealing anisotropy in water diffusion, with a greater tendency for water to move parallel to the film. The authors claimed that the increased hydrophobicity of the carbon increased this anisotropy.…”

Section: Introductionmentioning

confidence: 99%

Mesoscale simulations of confined Nafion thin films

Vanya

Sharman

Elliott

2017

The Journal of Chemical Physics

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The morphology and transport properties of thin films of the ionomer Nafion, with thicknesses on the order of the bulk cluster size, have been investigated as a model system to explain the anomalous behaviour of catalyst/electrode-polymer interfaces in membrane-electrode assemblies. We have employed dissipative particle dynamics (DPD) to investigate the interaction of water and fluorocarbon chains with carbon and quartz as confining materials for a wide range of operational water contents and film thicknesses. We found confinement-induced clustering of water perpendicular to the thin film. Hydrophobic carbon forms a water depletion zone near the film interface, whereas hydrophilic quartz results in a zone with excess water. There are, on average, oscillating water-rich and fluorocarbon-rich regions, in agreement with experimental results from neutron reflectometry. Water diffusivity shows increasing directional anisotropy of up to 30% with decreasing film thickness, depending of the confining material. The percolation analysis revealed significant differences in water clustering and connectivity with the confining material. These findings indicate the fundamentally different nature of ionomer thin films, compared to membranes, and suggest explanations for increased ionic resistances observed in the catalyst layer.

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Prediction of anisotropic transport in Nafion containing catalyst layers

Cited by 32 publications

References 11 publications

Morphology and diffusion within model membranes: Application of bond counting method to architectures with bimodal side chain length distributions

Morphology and diffusion within model membranes: Application of bond counting method to architectures with bimodal side chain length distributions

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

Mesoscale simulations of confined Nafion thin films

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