Elucidating the Ionomer-Electrified Metal Interface

Kendrick, Ian; Kumari, Dunesh; Yakaboski, Adam; Dimakis, Nicholas; Smotkin, Eugene S.

doi:10.1021/ja1081487

Cited by 105 publications

(168 citation statements)

References 29 publications

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“…This mode has been established to be dominated by motions of the Nafion exchange site in the sulfonic acid form that has no local symmetry (C 1 ). 22,[48][49][50] At potentials negative of 700 mV, Raman bands at 1066 cm −1 and 969 cm −1 emerge. These bands, also observed in the hydrated Nafion (red) IR spectrum, are the C 3V, HF and C 3V, LF group modes respectively.…”

Section: Resultsmentioning

confidence: 99%

“…These group modes are consequent of a dissociated Nafion exchange site (sulfonate form) with C 3V local symmetry. 22,48,[51][52][53][54][55] C 1 normal mode eigenvector animation snapshots.-The dehydrated Nafion spectrum (blue) features bands at 1414 cm −1 and 910 cm −1 . These are group modes that have motional participation of the exchange group in the sulfonic acid form (C 1 local symmetry).…”

Section: Resultsmentioning

confidence: 99%

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Operando Raman Micro-Spectroscopy of Polymer Electrolyte Fuel Cells

Kendrick

Fore

Doan

et al. 2016

J. Electrochem. Soc.

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Operando Raman micro-spectroscopy of the membrane electrode assembly (MEA) of a fully operating hydrogen/oxygen Nafion electrolyte fuel cell is described. Coarse depth profiling of the fuel cell system enabled appropriate positioning of the microspectroscopy laser focal point for MEA catalytic layer spectroscopy. An increase in the ionomer state-of-hydration, from oxygen reduction at the cathode, transitions ion exchange sites from the sulfonic acid to the dissociated sulfonate form. Visualization of density functional theory calculated normal mode eigenvector animations enabled assignments of Nafion side-chain vibrational bands in terms of the exchange site local symmetry: C 1 and C 3V modes correlate to the sulfonic acid and sulfonate forms respectively. The gradual transition of the MEA spectra from C 1 to C 3V modes, from the fuel cell open circuit voltage to the short circuit current respectively, demonstrate the utility of vibrational group mode assignments in terms of exchange site local symmetry.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Operando Raman Micro-Spectroscopy of Polymer Electrolyte Fuel Cells

Kendrick

Fore

Doan

et al. 2016

J. Electrochem. Soc.

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“…3N- 6 10 normal modes, for both repeat units, were used to assign IR bands. [29,31] The C 3V group modes (C 3V, 11 HF ; 1061 cm -1 and C 3V, LF ; 969 cm -1 ) arise from the same set of Nafion side-chain functional groups un-12 der fully hydrated conditions. The high frequency (HF) mode is dominated by a COC-A asymmetric 13 stretch.…”

Section: Manuscriptmentioning

confidence: 99%

“…This has been discussed previously. [31] The partial positive charge on the 8 sulfur decreases upon complexation with Li + and the partial negative charges on the oxygen atoms are 9 reduced due to the delocalization of charge to Li + . Clearly Li + symmetrizes the charge distribution 10 somewhat and lowers the overall dipole moment along the 3-fold axis.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Symmetry-based IR group modes as dynamic probes of Nafion ion exchange site structure

Doan

Navarro²,

Kumari

et al. 2015

Polymer

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“…He also found that the CF3CF3 groups are also strongly bound. [54] In this study we studied various adsorbed species on Pt, including water, oxygen, hydronium, and various Nafion fragments. From these simulations, we built a computational system to study the three-phase interface of a PEMFC.…”

Section: De-ee0000466 Ballard Materials Products Incmentioning

confidence: 99%

Final Project Report: Development of Micro-Structural Mitigation Strategies for PEM Fuel Cells: Morphological Simulations and Experimental Approaches

Wessel¹,

Harvey²

2013

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The overall objectives of this project were to improve the understanding of the design space of fuel cell materials and components and to recommend degradation mitigation strategies that facilitate the achievement of the 2020 technical targets. The deliverables from this project to the public, fuel cell community, and DOE are an open-source code fuel cell performance and durability model including a user-guide for dissemination and use within the public domain, and catalyst layer performance and durability correlations with identification of the design spaces relevant to improved durability.The project was led by Ballard Material Products via a direct subcontract to Ballard Power Systems and included critical contributions from the other subcontractors: Georgia Institute of Technology, Los Alamos National Laboratory, Michigan Technical University, Queen's University/University of Calgary, and the University of New Mexico. Ballard's work, which encompassed the development of the performance and degradation models as well as experimental investigation for model validation and the correlation/durability window development, was carried out at Ballard Power Systems' facility in Burnaby, B.C., Canada.Ballard recognizes the significant contribution made by each of the project collaborators and their respective team members. As well, Ballard recognizes the support provided from the DOE project managers, Dr. David Peterson and Kathi Epping Martin, and the project technical advisor, Dr. John Kopasz.The work was funded by the U.S. Department of Energy, Energy Efficiency and Renewable Energy. DE-EE0000466Ballard Material Products Inc. Chapter IPage iii EXECUTIVE SUMMARYThe durability of PEM fuel cells is a primary requirement for large scale commercialization of these power systems in transportation and stationary market applications that target operational lifetimes of 5,000 hours and 40,000 hours by 2015, respectively. Key degradation modes contributing to fuel cell lifetime limitations have been largely associated with the platinum-based cathode catalyst layer. Furthermore, as fuel cells are driven to low cost materials and lower catalyst loadings in order to meet the cost targets for commercialization, the catalyst durability has become even more important. While over the past few years significant progress has been made in identifying the underlying causes of fuel cell degradation and key parameters that greatly influence the degradation rates, many gaps with respect to knowledge of the driving mechanisms still exist; in particular, the acceleration of the mechanisms due to different structural compositions and under different fuel cell conditions remains an area not well understood.The focus of this project was to address catalyst durability by using a dual path approach that coupled an extensive range of experimental analysis and testing with a multi-scale modeling approach. With this, the major technical areas/issues of catalyst and catalyst layer performance and durability that were addressed are:1. Catalyst and ca...

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Elucidating the Ionomer-Electrified Metal Interface

Cited by 105 publications

References 29 publications

Operando Raman Micro-Spectroscopy of Polymer Electrolyte Fuel Cells

Operando Raman Micro-Spectroscopy of Polymer Electrolyte Fuel Cells

Symmetry-based IR group modes as dynamic probes of Nafion ion exchange site structure

Final Project Report: Development of Micro-Structural Mitigation Strategies for PEM Fuel Cells: Morphological Simulations and Experimental Approaches

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