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@PHDTHESIS{Meise:1044140,
      author       = {Meise, Ansgar},
      title        = {{I}nvestigation of {D}ynamic {M}aterial {C}hanges {D}uring
                      the {P}reparation of {Z}n{P}d {N}anoparticles {S}upported on
                      {Z}n{O} and their {C}atalytic {A}pplication in {M}ethanol
                      {S}team {R}eforming onthe {A}tomic {L}evel},
      volume       = {670},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2025-03042},
      isbn         = {978-3-95806-838-4},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {xviii, 175},
      year         = {2025},
      note         = {Dissertation, RWTH Aachen University, 2025},
      abstract     = {Given its high energy density and sustainability, hydrogen
                      is regarded as a crucial energy carrier in the pursuit of a
                      carbon-free energy economy. In the search for a storage
                      medium of hydrogen, methanol is emerging as a promising
                      chemical storage. The recovery of hydrogen is achieved
                      through the process of methanol steam reforming, whereby
                      methanol and water are transformed into hydrogen and carbon
                      dioxide. The intermetallic ZnPd nanoparticle supported on
                      ZnO has been demonstrated to function as an excellent
                      catalyst for the reforming, due to its high CO₂
                      selectivity and activity. However, the favourable catalytic
                      performance is first established during catalysis. The
                      reason for the enhancement of the catalytic properties
                      appears to be a dynamic structural evolution of the
                      catalyst, as evidenced by the formation of ZnO patches. The
                      nanostructural dynamics and the underlying cause of the
                      improved catalytic properties can be elucidated by analysing
                      the synthesis and catalysis of the catalytic system in situ.
                      The comprehensive work studies the preparation, structural
                      evolution, and catalytic application of ZnPd nanoparticles
                      supported on ZnO during methanol steam reforming (MSR),
                      using in situ scanning transmission electron microscopy
                      (STEM). The preparation stages, including calcination of
                      supported palladium nitrate and reduction of palladium
                      oxide, were analysed. In situ calcination revealed that
                      palladium nitrate transforms into palladium oxide at ~170
                      °C, leading to nanoparticle growth, with a stable size
                      window between 200-400 °C. At temperatures above 460 °C,
                      PdO decomposes into elemental palladium, triggering particle
                      mobility, agglomeration, and ZnO nanorod formation. Further
                      heating above 660 °C under high vacuum caused ZnO faceting
                      and decomposition, which was facilitated by the evaporation
                      of elemental zinc and oxygen. In situ reduction of supported
                      PdO resulted in the formation of intermetallic ZnPd via two
                      distinct formation mechanisms: hydrogen spillover-induced
                      ZnO migration and encapsulation of Pd nanoparticles,
                      followed by ZnPd nucleation and core-shell structure
                      formation. The findings align with those of ex situ
                      experiments and existing literature, confirming that the
                      electron beam enhances the reaction but does not activate
                      it. In situ STEM experiments in open and closed cell
                      configurations demonstrated that methanol acts as a strong
                      reducing agent for ZnO, while hydrogen and water steam
                      stabilise the system. Under MSR conditions, ZnPd
                      nanoparticles are subject to compositional and morphological
                      changes, including Zn enrichment and nanoparticle faceting.
                      The formation of ZnO patches, which was observed for the
                      first time in situ, was found to preferentially occur on
                      ZnPd facets and Znenriched areas. This formation requires a
                      precise balance between hydrogen, water, and methanol and
                      thus is sensitively dependent on the chemical potential. The
                      research provides novel insights into the dynamic behaviour
                      of ZnPd/ZnO catalysts under operational conditions,
                      advancing the methodology for studying catalysts in steam
                      environments and contributing to the broader understanding
                      of catalytic systems.},
      cin          = {ER-C-1},
      cid          = {I:(DE-Juel1)ER-C-1-20170209},
      pnm          = {5351 - Platform for Correlative, In Situ and Operando
                      Characterization (POF4-535)},
      pid          = {G:(DE-HGF)POF4-5351},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2508051154384.680632860357},
      doi          = {10.34734/FZJ-2025-03042},
      url          = {https://juser.fz-juelich.de/record/1044140},
}