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@ARTICLE{Olbrich:1014734,
      author       = {Olbrich, Wolfgang and Kadyk, T. and Sauter, U. and
                      Eikerling, M. and Gostick, J.},
      title        = {{S}tructure and conductivity of ionomer in {PEM} fuel cell
                      catalyst layers: a model-based analysis},
      journal      = {Scientific reports},
      volume       = {13},
      number       = {1},
      issn         = {2045-2322},
      address      = {[London]},
      publisher    = {Macmillan Publishers Limited, part of Springer Nature},
      reportid     = {FZJ-2023-03424},
      pages        = {14127},
      year         = {2023},
      abstract     = {Efforts in design and optimization of catalyst layers for
                      polymer electrolyte fuel cells hinge on mathematical models
                      that link electrode composition and microstructure with
                      effective physico-chemical properties. A pivotal property of
                      these layers and the focus of this work is the proton
                      conductivity, which is largely determined by the morphology
                      of the ionomer. However, available relations between
                      catalyst layer composition and proton conductivity are often
                      adopted from general theories for random heterogeneous media
                      and ignore specific features of the microstructure, e.g.,
                      agglomerates, film-like structures, or the hierarchical
                      porous network. To establish a comprehensive understanding
                      of the peculiar structure-property relations, we generated
                      synthetic volumetric images of the catalyst layer
                      microstructure. In a mesoscopic volume element, we modeled
                      the electrolyte phase and calculated the proton conductivity
                      using numerical tools. Varying the ionomer morphology in
                      terms of ionomer film coverage and thickness revealed two
                      limiting cases: the ionomer can either form a thin film with
                      high coverage on the catalyst agglomerates; or the ionomer
                      exists as voluminous chunks that connect across the
                      inter-agglomerate space. Both cases were modeled
                      analytically, adapting relations from percolation theory.
                      Based on the simulated data, a novel relation is proposed,
                      which links the catalyst layer microstructure to the proton
                      conductivity over a wide range of morphologies. The
                      presented analytical approach is a versatile tool for the
                      interpretation of experimental trends and it provides
                      valuable guidance for catalyst layer design. The proposed
                      model was used to analyze the formation of the catalyst
                      layer microstructure during the ink stage. A parameter study
                      of the initial ionomer film thickness and the ionomer
                      dispersion parameter revealed that the ionomer morphology
                      should be tweaked towards well-defined films with high
                      coverage of catalyst agglomerates. These implications match
                      current efforts in the experimental literature and they may
                      thus provide direction in electrode materials research for
                      polymer electrolyte fuel cells.},
      cin          = {IEK-13},
      ddc          = {600},
      cid          = {I:(DE-Juel1)IEK-13-20190226},
      pnm          = {1222 - Components and Cells (POF4-122)},
      pid          = {G:(DE-HGF)POF4-1222},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {37644035},
      UT           = {WOS:001119561800048},
      doi          = {10.1038/s41598-023-40637-0},
      url          = {https://juser.fz-juelich.de/record/1014734},
}