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Title: Fractal diffusion in high temperature polymer electrolyte fuel cell membranes

Abstract

In this paper, the performance of fuel cells depends largely on the proton diffusion in the proton conducting membrane, the core of a fuel cell. High temperature polymer electrolyte fuel cells are based on a polymer membrane swollen with phosphoric acid as the electrolyte, where proton conduction takes place. We studied the proton diffusion in such membranes with neutron scattering techniques which are especially sensitive to the proton contribution. Time of flight spectroscopy and backscattering spectroscopy have been combined to cover a broad dynamic range. In order to selectively observe the diffusion of protons potentially contributing to the ion conductivity, two samples were prepared, where in one of the samples the phosphoric acid was used with hydrogen replaced by deuterium. The scattering data from the two samples were subtracted in a suitable way after measurement. Thereby subdiffusive behavior of the proton diffusion has been observed and interpreted in terms of a model of fractal diffusion. For this purpose, a scattering function for fractal diffusion has been developed. The fractal diffusion dimension d w and the Hausdorff dimension d f have been determined on the length scales covered in the neutron scattering experiments.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]; ORCiD logo [1];  [3];  [2]; ORCiD logo [4]; ORCiD logo [4]; ORCiD logo [5];  [2];  [2]
  1. Forschungszentrum Julich GmbH, Garching (Germany)
  2. Forschungszentrum Julich GmbH, Julich (Germany)
  3. Forschungszentrum Julich GmbH, Julich (Germany); RWTH Aachen Univ., Aachen (Germany)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  5. Louisiana State Univ., Baton Rouge, LA (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1440817
Alternate Identifier(s):
OSTI ID: 1439395
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 148; Journal Issue: 20; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Hopfenmuller, Bernhard, Zorn, Reiner, Holderer, Olaf, Ivanova, Oxana, Lehnert, Werner, Luke, Wiebke, Ehlers, Georg, Jalarvo, Niina, Schneider, Gerald J., Monkenbusch, Michael, and Richter, Dieter. Fractal diffusion in high temperature polymer electrolyte fuel cell membranes. United States: N. p., 2018. Web. doi:10.1063/1.5018717.
Hopfenmuller, Bernhard, Zorn, Reiner, Holderer, Olaf, Ivanova, Oxana, Lehnert, Werner, Luke, Wiebke, Ehlers, Georg, Jalarvo, Niina, Schneider, Gerald J., Monkenbusch, Michael, & Richter, Dieter. Fractal diffusion in high temperature polymer electrolyte fuel cell membranes. United States. doi:10.1063/1.5018717.
Hopfenmuller, Bernhard, Zorn, Reiner, Holderer, Olaf, Ivanova, Oxana, Lehnert, Werner, Luke, Wiebke, Ehlers, Georg, Jalarvo, Niina, Schneider, Gerald J., Monkenbusch, Michael, and Richter, Dieter. Tue . "Fractal diffusion in high temperature polymer electrolyte fuel cell membranes". United States. doi:10.1063/1.5018717. https://www.osti.gov/servlets/purl/1440817.
@article{osti_1440817,
title = {Fractal diffusion in high temperature polymer electrolyte fuel cell membranes},
author = {Hopfenmuller, Bernhard and Zorn, Reiner and Holderer, Olaf and Ivanova, Oxana and Lehnert, Werner and Luke, Wiebke and Ehlers, Georg and Jalarvo, Niina and Schneider, Gerald J. and Monkenbusch, Michael and Richter, Dieter},
abstractNote = {In this paper, the performance of fuel cells depends largely on the proton diffusion in the proton conducting membrane, the core of a fuel cell. High temperature polymer electrolyte fuel cells are based on a polymer membrane swollen with phosphoric acid as the electrolyte, where proton conduction takes place. We studied the proton diffusion in such membranes with neutron scattering techniques which are especially sensitive to the proton contribution. Time of flight spectroscopy and backscattering spectroscopy have been combined to cover a broad dynamic range. In order to selectively observe the diffusion of protons potentially contributing to the ion conductivity, two samples were prepared, where in one of the samples the phosphoric acid was used with hydrogen replaced by deuterium. The scattering data from the two samples were subtracted in a suitable way after measurement. Thereby subdiffusive behavior of the proton diffusion has been observed and interpreted in terms of a model of fractal diffusion. For this purpose, a scattering function for fractal diffusion has been developed. The fractal diffusion dimension dw and the Hausdorff dimension df have been determined on the length scales covered in the neutron scattering experiments.},
doi = {10.1063/1.5018717},
journal = {Journal of Chemical Physics},
number = 20,
volume = 148,
place = {United States},
year = {2018},
month = {5}
}

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