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@INPROCEEDINGS{Kadyk:1022607,
      author       = {Kadyk, Thomas and Olbrich, Wolfgang and Bernhard, David and
                      Kirsch, Sebastian and Krewer, Ulrike and Eikerling, Michael},
      title        = {{B}ridging {M}icrostructure {D}egradation and {M}acroscopic
                      {P}erformance {M}odeling in {P}olymer {E}lectrolyte {F}uel
                      {C}ell {C}atalyst {L}ayers},
      reportid     = {FZJ-2024-01573},
      year         = {2023},
      abstract     = {Electrochemical energy devices like fuel cells,
                      electrolyzers or batteries harness porous electrodes with
                      complex heterogeneous microstructures to optimize the
                      interplay between the transport processes and
                      electrochemical reaction. The use of nano-to-microstructured
                      electrodes increases performance as well as catalyst
                      utilization. However, such electrode structures are also
                      more susceptible to degradation and performance decline.
                      Statistical-physical models for microstructure degradation
                      must be interlinked to macrohomogeneous performance models.
                      This talk outlines the challenges in establishing this link,
                      as depicted in Fig. 1, and discusses possible solutions.The
                      catalyst layer of a PEFC is a complex composite electrode of
                      Pt-based catalyst nanoparticles on a carbon substrate,
                      ionically connected by ionomer and water as the active
                      reaction medium. During operation, catalyst nanoparticles
                      undergo changes due to dissolution, re-deposition of
                      dissolved catalyst (i.e., Ostwald ripening), coagulation or
                      inactivation of catalyst particles. The carbon substrate can
                      undergo corrosion and the ionomer can undergo restructuring,
                      which could affect the water retention behavior of the
                      electrode. The changes in catalyst particle properties,
                      especially the particle radius distribution, lead to a
                      decrease of the overall catalyst surface available for the
                      reaction, and thus to a performance decline. At a first
                      glance, the coupling between microstructure and performance
                      could be achieved by using the catalyst surface area as a
                      scaling factor for the exchange current density. However,
                      difficulties arise when incorporating degradation mechanisms
                      that alter structural properties and conditions other than
                      the catalyst particle size. For example, dealloying of
                      catalysts like PtCo or PtNi changes both particles size and
                      materials composition. When deconvoluting both effects in
                      accelerated stress tests on automotive cells, we found that
                      the change in catalyst activity, described by Tafel slope
                      and exchange current density, correlates with the change in
                      active surface area [1]. Changes in the ionomer morphology
                      can lead to altered wetting behavior and liquid water
                      retention, leaving the catalyst layer more prone to flooding
                      [2]. Additionally, proton conductivity changes, but its
                      description needs to take structural features of the ionomer
                      morphology into account [3]. Overall, linking structural
                      degradation effects to device-level performance requires
                      finding and tailoring appropriate descriptors and structure
                      property relationships.References: [1] D. Bernhard, T.
                      Kadyk, S. Kirsch, H. Scholz, U. Krewer. J. Power Sources
                      562:232771 (2023)[2] W. Olbrich, T. Kadyk, U. Sauter, M.
                      Eikerling. Electrochim. Acta 431:140850 (2022)[3] W.
                      Olbrich, T. Kadyk, U. Sauter, M. Eikerling, J. Gostick.
                      Scientific Reports 13:14127 (2023)Keywords: polymer
                      electrolyte fuel cell, solid oxide cell, catalyst
                      degradation, modelling, voltage loss prediction.},
      month         = {Dec},
      date          = {2023-12-11},
      organization  = {World Fuel Cell Conference 2023,
                       London (UK), 11 Dec 2023 - 13 Dec 2023},
      subtyp        = {After Call},
      cin          = {IEK-13},
      cid          = {I:(DE-Juel1)IEK-13-20190226},
      pnm          = {1231 - Electrochemistry for Hydrogen (POF4-123)},
      pid          = {G:(DE-HGF)POF4-1231},
      typ          = {PUB:(DE-HGF)6},
      doi          = {10.34734/FZJ-2024-01573},
      url          = {https://juser.fz-juelich.de/record/1022607},
}