@article{7295,
  abstract     = {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.},
  author       = {Mourad, Eléonore and Coustan, Laura and Freunberger, Stefan Alexander and Mehdi, Ahmad and Vioux, André and Favier, Frédérique and Fontaine, Olivier},
  issn         = {0013-4686},
  journal      = {Electrochimica Acta},
  number       = {7},
  pages        = {513--523},
  publisher    = {Elsevier},
  title        = {{Biredox ionic liquids: Electrochemical investigation and impact of ion size on electron transfer}},
  doi          = {10.1016/j.electacta.2016.02.211},
  volume       = {206},
  year         = {2016},
}

@article{7320,
  abstract     = {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.},
  author       = {Flückiger, Reto and Freunberger, Stefan Alexander and Kramer, Denis and Wokaun, Alexander and Scherer, Günther G. and Büchi, Felix N.},
  issn         = {0013-4686},
  journal      = {Electrochimica Acta},
  number       = {2},
  pages        = {551--559},
  publisher    = {Elsevier},
  title        = {{Anisotropic, effective diffusivity of porous gas diffusion layer materials for PEFC}},
  doi          = {10.1016/j.electacta.2008.07.034},
  volume       = {54},
  year         = {2008},
}

@article{7330,
  abstract     = {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.},
  author       = {Santis, M. and Freunberger, Stefan Alexander and Reiner, A. and Büchi, F.N.},
  issn         = {0013-4686},
  journal      = {Electrochimica Acta},
  number       = {25},
  pages        = {5383--5393},
  publisher    = {Elsevier},
  title        = {{Homogenization of the current density in polymer electrolyte fuel cells by in-plane cathode catalyst gradients}},
  doi          = {10.1016/j.electacta.2006.02.008},
  volume       = {51},
  year         = {2006},
}