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@ARTICLE{Heymann:906785,
      author       = {Heymann, Lisa and Weber, Moritz L. and Wohlgemuth, Marcus
                      and Risch, Marcel and Dittmann, Regina and Baeumer,
                      Christoph and Gunkel, Felix},
      title        = {{S}eparating the {E}ffects of {B}and {B}ending and
                      {C}ovalency in {H}ybrid {P}erovskite {O}xide
                      {E}lectrocatalyst {B}ilayers for {W}ater {E}lectrolysis},
      journal      = {ACS applied materials $\&$ interfaces},
      volume       = {14},
      number       = {12},
      issn         = {1944-8244},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {FZJ-2022-01692},
      pages        = {14129–14136},
      year         = {2022},
      abstract     = {The Co–O covalency in perovskite oxide cobaltites such as
                      La1–xSrxCoO3 is believed to impact the electrocatalytic
                      activity during electrochemical water splitting at the anode
                      where the oxygen evolution reaction (OER) takes place.
                      Additionally, space charge layers through band bending at
                      the interface to the electrolyte may affect the electron
                      transfer into the electrode, complicating the analysis and
                      identification of true OER activity descriptors. Here, we
                      separate the influence of covalency and band bending in
                      hybrid epitaxial bilayer structures of highly OER-active
                      La0.6Sr0.4CoO3 and undoped and less-active LaCoO3. Ultrathin
                      LaCoO3 capping layers of 2–8 unit cells on La0.6Sr0.4CoO3
                      show intermediate OER activity between La0.6Sr0.4CoO3 and
                      LaCoO3 evidently caused by the increased surface Co–O
                      covalency compared to single LaCoO3 as detected by X-ray
                      photoelectron spectroscopy. A Mott–Schottkyanalysis
                      revealed low flat band potentials for different LaCoO3
                      capping layer thicknesses, indicating that no limiting
                      extended space charge layer exists under OER conditions as
                      all catalyst bilayer films exhibited hole accumulation at
                      the surface. The combined X-ray photoelectron spectroscopy
                      and Mott–Schottky analysis thus enables us to
                      differentiate between the influence of the covalency and
                      intrinsic space charge layers, which are indistinguishable
                      in a single physical or electrochemical characterization.
                      Our results emphasize the prominent role of transition metal
                      oxygen covalency in perovskite electrocatalysts and
                      introduce a bilayer approach to fine-tune the surface
                      electronic structure.},
      cin          = {PGI-7 / PGI-10 / JARA-FIT},
      ddc          = {600},
      cid          = {I:(DE-Juel1)PGI-7-20110106 / I:(DE-Juel1)PGI-10-20170113 /
                      $I:(DE-82)080009_20140620$},
      pnm          = {5233 - Memristive Materials and Devices (POF4-523) / DFG
                      project 167917811 - SFB 917: Resistiv schaltende
                      Chalkogenide für zukünftige Elektronikanwendungen:
                      Struktur, Kinetik und Bauelementskalierung "Nanoswitches"
                      (167917811)},
      pid          = {G:(DE-HGF)POF4-5233 / G:(GEPRIS)167917811},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000787374700013},
      doi          = {10.1021/acsami.1c20337},
      url          = {https://juser.fz-juelich.de/record/906785},
}