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@PHDTHESIS{Liu:905047,
      author       = {Liu, Chang},
      title        = {{N}oble {M}etal {C}oated {P}orous {T}ransport {L}ayers for
                      {P}olymer {E}lectrolyte {M}embrane {W}ater {E}lectrolysis},
      volume       = {562},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2022-00346},
      isbn         = {978-3-95806-603-8},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {139},
      year         = {2021},
      note         = {Dissertation, RWTH Aachen University, 2021},
      abstract     = {Polymer electrolyte membrane (PEM) water electrolyzers are
                      electrochemical energyconversion devices that split water
                      into its constituent elements of hydrogen and oxygen.
                      Titaniumbasedporous transport layers (PTL) are widely used
                      due to their good bulk conductivity, highcorrosion
                      resistivity, and excellent mechanical strength. However,
                      titanium-based PTLs situatedat the anode side of PEM
                      electrolyzers are subjected to harsh oxidizing conditions
                      such as highanode overpotential, low pH and oxygen
                      evolution. Under these conditions, titanium (Ti0) changesits
                      oxidation state over time, which induces the formation of a
                      thin but continuously growing layerof passivated titanium
                      (TiOx). Consequently, the contact resistance of titanium
                      PTLs is adverselyaffected, critically decreasing cell
                      performance and durability.In this thesis, a very simple and
                      scalable method is used to protect the titanium-based PTL
                      frompassivation by sputtering very thin layers of noble
                      metal coatings such as Ir, Pt, or Au onto thePTLs. The 20 to
                      50 nm thick noble metal coatings on the titanium fibers
                      significantly decreasedinterfacial contact resistance
                      between the PTL and catalyst layer, and improved cell
                      performance.The single cells assembled with Ir- or Pt-coated
                      PTLs delivered higher cell performance than cellswith
                      Au-coated PTLs, and nearly identical cell performance as
                      carbon paper, which is prone tocarbon corrosion under these
                      operating conditions.The high cost of using noble metal
                      coatings can be decreased by reducing the loading of
                      thenoble metals. The loading of Ir as a protective layer on
                      the PTL has an impact on the cellperformance. The amount of
                      iridium on one side of the PTL was reduced to 0.025
                      mgIr∙cm-2 andshowed identical cell performance as
                      Ir-coated PTLs with higher iridium loading, whicheffectively
                      reduced the cost of the Ir. The total amount of iridium is
                      40 times less compared towhat is usually used in an anode
                      catalyst layer, and 20 times less than Au or Pt typically
                      used asprotective layers in contemporary and commercial
                      electrolyzers.The critical passivation of the bare
                      titanium-based PTL is also one significant factor
                      thatrestricts the durability of a PEM water electrolyzer. In
                      order to investigate the durability of noblemetal coatings
                      (Ir, Pt, Au) on the PTLs, a series of long-term measurements
                      were performed under2 V and 80 °C on the single cells
                      assembled with Ir-coated, Pt-coated and Au-coated
                      PTLs,respectively. Compared to the cell without the
                      coatings, the cell assembled with iridium andplatinum
                      coatings showed degradation rates close to zero, while the
                      identical cell performance wasobserved after 4000 hours with
                      a cell voltage of 2 V. These results demonstrate that
                      iridium andplatinum coatings on titanium-based PTLs are
                      highly effective at protecting the PTL againstpassivation,
                      ultimately improving cell performance and durability.},
      cin          = {IEK-14},
      cid          = {I:(DE-Juel1)IEK-14-20191129},
      pnm          = {1231 - Electrochemistry for Hydrogen (POF4-123)},
      pid          = {G:(DE-HGF)POF4-1231},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2022020848},
      url          = {https://juser.fz-juelich.de/record/905047},
}