---
_id: '7295'
abstract:
- lang: eng
  text: Redox ionic liquids consisting of ions bearing redox moieties are receiving
    increasing interest in electrochemical applications, as they associate electroactive
    properties with the classical properties of ionic liquids. Here, biredox ionic
    liquid electrolytes are described in which both anion and cation are functionalized
    with anthraquinone and 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) groups, respectively.
    In-depth investigations based on crossed experimental and theoretical studies
    were carried out to elucidate how the bulkiness of ions bearing a redox moiety
    impacted electron and mass transfers, and accordingly the efficiency of electrochemical
    devices. The values of solvated radii of different redox ions, as well as the
    related kinetic constants, were extracted from cyclic voltammetry experiments.
    Reformulating the basic relations of electron transfer theory (based on Marcus-Hush
    theory) evidenced that in such redox species, with an unsymmetrical located redox
    centre, the electron transfer was not governed by the overall size of the solvated
    redox species, but rather by the radius of the redox active subunit, which takes
    preferential orientation towards the surface, thus allowing higher kinetic constants
    than what classical theory would predict. This vision opens ample opportunities
    for biredox ILs as electrolytes in electrochemical devices.
article_processing_charge: No
article_type: original
author:
- first_name: Eléonore
  full_name: Mourad, Eléonore
  last_name: Mourad
- first_name: Laura
  full_name: Coustan, Laura
  last_name: Coustan
- first_name: Stefan Alexander
  full_name: Freunberger, Stefan Alexander
  id: A8CA28E6-CE23-11E9-AD2D-EC27E6697425
  last_name: Freunberger
  orcid: 0000-0003-2902-5319
- first_name: Ahmad
  full_name: Mehdi, Ahmad
  last_name: Mehdi
- first_name: André
  full_name: Vioux, André
  last_name: Vioux
- first_name: Frédérique
  full_name: Favier, Frédérique
  last_name: Favier
- first_name: Olivier
  full_name: Fontaine, Olivier
  last_name: Fontaine
citation:
  ama: 'Mourad E, Coustan L, Freunberger SA, et al. Biredox ionic liquids: Electrochemical
    investigation and impact of ion size on electron transfer. <i>Electrochimica Acta</i>.
    2016;206(7):513-523. doi:<a href="https://doi.org/10.1016/j.electacta.2016.02.211">10.1016/j.electacta.2016.02.211</a>'
  apa: 'Mourad, E., Coustan, L., Freunberger, S. A., Mehdi, A., Vioux, A., Favier,
    F., &#38; Fontaine, O. (2016). Biredox ionic liquids: Electrochemical investigation
    and impact of ion size on electron transfer. <i>Electrochimica Acta</i>. Elsevier.
    <a href="https://doi.org/10.1016/j.electacta.2016.02.211">https://doi.org/10.1016/j.electacta.2016.02.211</a>'
  chicago: 'Mourad, Eléonore, Laura Coustan, Stefan Alexander Freunberger, Ahmad Mehdi,
    André Vioux, Frédérique Favier, and Olivier Fontaine. “Biredox Ionic Liquids:
    Electrochemical Investigation and Impact of Ion Size on Electron Transfer.” <i>Electrochimica
    Acta</i>. Elsevier, 2016. <a href="https://doi.org/10.1016/j.electacta.2016.02.211">https://doi.org/10.1016/j.electacta.2016.02.211</a>.'
  ieee: 'E. Mourad <i>et al.</i>, “Biredox ionic liquids: Electrochemical investigation
    and impact of ion size on electron transfer,” <i>Electrochimica Acta</i>, vol.
    206, no. 7. Elsevier, pp. 513–523, 2016.'
  ista: 'Mourad E, Coustan L, Freunberger SA, Mehdi A, Vioux A, Favier F, Fontaine
    O. 2016. Biredox ionic liquids: Electrochemical investigation and impact of ion
    size on electron transfer. Electrochimica Acta. 206(7), 513–523.'
  mla: 'Mourad, Eléonore, et al. “Biredox Ionic Liquids: Electrochemical Investigation
    and Impact of Ion Size on Electron Transfer.” <i>Electrochimica Acta</i>, vol.
    206, no. 7, Elsevier, 2016, pp. 513–23, doi:<a href="https://doi.org/10.1016/j.electacta.2016.02.211">10.1016/j.electacta.2016.02.211</a>.'
  short: E. Mourad, L. Coustan, S.A. Freunberger, A. Mehdi, A. Vioux, F. Favier, O.
    Fontaine, Electrochimica Acta 206 (2016) 513–523.
date_created: 2020-01-15T12:16:17Z
date_published: 2016-07-10T00:00:00Z
date_updated: 2021-01-12T08:12:50Z
day: '10'
doi: 10.1016/j.electacta.2016.02.211
extern: '1'
intvolume: '       206'
issue: '7'
language:
- iso: eng
month: '07'
oa_version: None
page: 513-523
publication: Electrochimica Acta
publication_identifier:
  issn:
  - 0013-4686
publication_status: published
publisher: Elsevier
quality_controlled: '1'
status: public
title: 'Biredox ionic liquids: Electrochemical investigation and impact of ion size
  on electron transfer'
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 206
year: '2016'
...
---
_id: '7320'
abstract:
- lang: eng
  text: A comparative, experimental diffusivity study of gas diffusion layer (GDL)
    materials for polymer electrolyte fuel cells (PEFC) is presented for the first
    time. The GDL plays an important role for electrochemical losses due to gas transport
    limitations at high current densities. Characterization and optimization of these
    layers is therefore essential to improve power density. A recently developed method
    which allows for fast diffusimetry is applied and data compared to the literature
    values. Measurements are made as a function of direction and compression and the
    effect of different binder structures and hydrophobic treatments on effective
    diffusivities are discussed. A better understanding of the results is gained by
    including novel GDL cross-section images and a meaningful unit cell model for
    the interpretation of the data. The diffusivity data is valuable for GDL manufacturers
    and future PEFC models. The study reveals that a binder–fiber ratio larger than
    50% has a negative impact on the effective diffusion properties. The hydrophobic
    treatment which is necessary to improve the water management can impede diffusion
    and thus reduce the power density. Furthermore binder has an isotropic effect
    while compression pronounces the in-plane orientation of the fibers.
article_processing_charge: No
article_type: original
author:
- first_name: Reto
  full_name: Flückiger, Reto
  last_name: Flückiger
- first_name: Stefan Alexander
  full_name: Freunberger, Stefan Alexander
  id: A8CA28E6-CE23-11E9-AD2D-EC27E6697425
  last_name: Freunberger
  orcid: 0000-0003-2902-5319
- first_name: Denis
  full_name: Kramer, Denis
  last_name: Kramer
- first_name: Alexander
  full_name: Wokaun, Alexander
  last_name: Wokaun
- first_name: Günther G.
  full_name: Scherer, Günther G.
  last_name: Scherer
- first_name: Felix N.
  full_name: Büchi, Felix N.
  last_name: Büchi
citation:
  ama: Flückiger R, Freunberger SA, Kramer D, Wokaun A, Scherer GG, Büchi FN. Anisotropic,
    effective diffusivity of porous gas diffusion layer materials for PEFC. <i>Electrochimica
    Acta</i>. 2008;54(2):551-559. doi:<a href="https://doi.org/10.1016/j.electacta.2008.07.034">10.1016/j.electacta.2008.07.034</a>
  apa: Flückiger, R., Freunberger, S. A., Kramer, D., Wokaun, A., Scherer, G. G.,
    &#38; Büchi, F. N. (2008). Anisotropic, effective diffusivity of porous gas diffusion
    layer materials for PEFC. <i>Electrochimica Acta</i>. Elsevier. <a href="https://doi.org/10.1016/j.electacta.2008.07.034">https://doi.org/10.1016/j.electacta.2008.07.034</a>
  chicago: Flückiger, Reto, Stefan Alexander Freunberger, Denis Kramer, Alexander
    Wokaun, Günther G. Scherer, and Felix N. Büchi. “Anisotropic, Effective Diffusivity
    of Porous Gas Diffusion Layer Materials for PEFC.” <i>Electrochimica Acta</i>.
    Elsevier, 2008. <a href="https://doi.org/10.1016/j.electacta.2008.07.034">https://doi.org/10.1016/j.electacta.2008.07.034</a>.
  ieee: R. Flückiger, S. A. Freunberger, D. Kramer, A. Wokaun, G. G. Scherer, and
    F. N. Büchi, “Anisotropic, effective diffusivity of porous gas diffusion layer
    materials for PEFC,” <i>Electrochimica Acta</i>, vol. 54, no. 2. Elsevier, pp.
    551–559, 2008.
  ista: Flückiger R, Freunberger SA, Kramer D, Wokaun A, Scherer GG, Büchi FN. 2008.
    Anisotropic, effective diffusivity of porous gas diffusion layer materials for
    PEFC. Electrochimica Acta. 54(2), 551–559.
  mla: Flückiger, Reto, et al. “Anisotropic, Effective Diffusivity of Porous Gas Diffusion
    Layer Materials for PEFC.” <i>Electrochimica Acta</i>, vol. 54, no. 2, Elsevier,
    2008, pp. 551–59, doi:<a href="https://doi.org/10.1016/j.electacta.2008.07.034">10.1016/j.electacta.2008.07.034</a>.
  short: R. Flückiger, S.A. Freunberger, D. Kramer, A. Wokaun, G.G. Scherer, F.N.
    Büchi, Electrochimica Acta 54 (2008) 551–559.
date_created: 2020-01-15T12:21:36Z
date_published: 2008-12-30T00:00:00Z
date_updated: 2021-01-12T08:13:02Z
day: '30'
doi: 10.1016/j.electacta.2008.07.034
extern: '1'
intvolume: '        54'
issue: '2'
language:
- iso: eng
month: '12'
oa_version: None
page: 551-559
publication: Electrochimica Acta
publication_identifier:
  issn:
  - 0013-4686
publication_status: published
publisher: Elsevier
quality_controlled: '1'
status: public
title: Anisotropic, effective diffusivity of porous gas diffusion layer materials
  for PEFC
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 54
year: '2008'
...
---
_id: '7330'
abstract:
- lang: eng
  text: Polymer electrolyte fuel cells (PE fuel cells) working with air at low stoichiometries
    (<2.0) and standard electrochemical components show a high degree of inhomogeneity
    in the current density distribution over the active area. An inhomogeneous current
    density distribution leads to a non-uniform utilization of the active area, which
    could negatively affect the time of life of the cells. Furthermore, it is also
    believed to lower cell performance. In this work, the homogenization of the current
    density, realized by means of tailored cathodes with along-the-air-channel redistributed
    catalyst loadings, is investigated. The air stoichiometry range for which a homogenization
    of the current density is achieved depends upon the gradient with which the catalyst
    is redistributed along the air channel. A gentle increasing catalyst loading profile
    homogenizes the current density at relatively higher air stoichiometries, while
    a steeper profile is suited better for lower air stoichiometries. The results
    show that a homogenization of the current density by means of redistributed catalyst
    loading has negative effects on cell performance. Model calculations corroborate
    the experimental findings on homogenization of the current density and deliver
    an explanation for the decrease in cell performance.
article_processing_charge: No
article_type: original
author:
- first_name: M.
  full_name: Santis, M.
  last_name: Santis
- first_name: Stefan Alexander
  full_name: Freunberger, Stefan Alexander
  id: A8CA28E6-CE23-11E9-AD2D-EC27E6697425
  last_name: Freunberger
  orcid: 0000-0003-2902-5319
- first_name: A.
  full_name: Reiner, A.
  last_name: Reiner
- first_name: F.N.
  full_name: Büchi, F.N.
  last_name: Büchi
citation:
  ama: Santis M, Freunberger SA, Reiner A, Büchi FN. Homogenization of the current
    density in polymer electrolyte fuel cells by in-plane cathode catalyst gradients.
    <i>Electrochimica Acta</i>. 2006;51(25):5383-5393. doi:<a href="https://doi.org/10.1016/j.electacta.2006.02.008">10.1016/j.electacta.2006.02.008</a>
  apa: Santis, M., Freunberger, S. A., Reiner, A., &#38; Büchi, F. N. (2006). Homogenization
    of the current density in polymer electrolyte fuel cells by in-plane cathode catalyst
    gradients. <i>Electrochimica Acta</i>. Elsevier. <a href="https://doi.org/10.1016/j.electacta.2006.02.008">https://doi.org/10.1016/j.electacta.2006.02.008</a>
  chicago: Santis, M., Stefan Alexander Freunberger, A. Reiner, and F.N. Büchi. “Homogenization
    of the Current Density in Polymer Electrolyte Fuel Cells by In-Plane Cathode Catalyst
    Gradients.” <i>Electrochimica Acta</i>. Elsevier, 2006. <a href="https://doi.org/10.1016/j.electacta.2006.02.008">https://doi.org/10.1016/j.electacta.2006.02.008</a>.
  ieee: M. Santis, S. A. Freunberger, A. Reiner, and F. N. Büchi, “Homogenization
    of the current density in polymer electrolyte fuel cells by in-plane cathode catalyst
    gradients,” <i>Electrochimica Acta</i>, vol. 51, no. 25. Elsevier, pp. 5383–5393,
    2006.
  ista: Santis M, Freunberger SA, Reiner A, Büchi FN. 2006. Homogenization of the
    current density in polymer electrolyte fuel cells by in-plane cathode catalyst
    gradients. Electrochimica Acta. 51(25), 5383–5393.
  mla: Santis, M., et al. “Homogenization of the Current Density in Polymer Electrolyte
    Fuel Cells by In-Plane Cathode Catalyst Gradients.” <i>Electrochimica Acta</i>,
    vol. 51, no. 25, Elsevier, 2006, pp. 5383–93, doi:<a href="https://doi.org/10.1016/j.electacta.2006.02.008">10.1016/j.electacta.2006.02.008</a>.
  short: M. Santis, S.A. Freunberger, A. Reiner, F.N. Büchi, Electrochimica Acta 51
    (2006) 5383–5393.
date_created: 2020-01-15T12:23:34Z
date_published: 2006-07-01T00:00:00Z
date_updated: 2021-01-12T08:13:07Z
day: '01'
doi: 10.1016/j.electacta.2006.02.008
extern: '1'
intvolume: '        51'
issue: '25'
language:
- iso: eng
month: '07'
oa_version: None
page: 5383-5393
publication: Electrochimica Acta
publication_identifier:
  issn:
  - 0013-4686
publication_status: published
publisher: Elsevier
quality_controlled: '1'
status: public
title: Homogenization of the current density in polymer electrolyte fuel cells by
  in-plane cathode catalyst gradients
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 51
year: '2006'
...