title: Operando X-ray Investigation of Electrode/Electrolyte Interfaces in Model Solid Oxide Fuel Cells.
abstract: We employed operando anomalous surface X-ray diffraction to investigate the buried interface between the cathode and the electrolyte of a model solid oxide fuel cell with atomic resolution. The cell was studied under different oxygen pressures at elevated temperatures and polarizations by external potential control. Making use of anomalous X-ray diffraction effects at the Y and Zr K-edges allowed us to resolve the interfacial structure and chemical composition of a (100)-oriented, 9.5 mol % yttria-stabilized zirconia (YSZ) single crystal electrolyte below a La0.6Sr0.4CoO3-δ(LSC) electrode. We observe yttrium segregation toward the YSZ/LSC electrolyte/electrode interface under reducing conditions. Under oxidizing conditions, the interface becomes Y depleted. The yttrium segregation is corroborated by an enhanced outward relaxation of the YSZ interfacial metal ion layer. At the same time, an increase in point defect concentration in the electrolyte at the interface was observed, as evidenced by reduced YSZ crystallographic site occupancies for the cations as well as the oxygen ions. Such changes in composition are expected to strongly influence the oxygen ion transport through this interface which plays an important role for the performance of solid oxide fuel cells. The structure of the interface is compared to the bare YSZ(100) surface structure near the microelectrode under identical conditions and to the structure of the YSZ(100) surface prepared under ultrahigh vacuum conditions.
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany; Fachbereich Physik, Universität Hamburg, Jungiusstr. 9, 20355 Hamburg, Germany.
authors.forename: Sergey
authors.initials: S
authors.lastname: Volkov
authors.affiliation: Deutsches Elektronen-Synchrotron DESY , Notkestr. 85, 22607 Hamburg, Germany.
authors.forename: Vedran
authors.initials: V
authors.lastname: Vonk
authors.affiliation: Max-Planck-Institut für Intelligente Systeme (former Max-Planck-Institut für Metallforschung), Heisenbergstr. 3, 70569 Stuttgart, Germany.
authors.forename: Navid
authors.initials: N
authors.lastname: Khorshidi
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany; Fachbereich Physik, Universität Hamburg, Jungiusstr. 9, 20355 Hamburg, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Franz
authors.affiliation: Vienna University of Technology , Institute of Chemical Technologies and Analytics, Getreidemarkt 9, A-1060 Vienna, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Kubicek
authors.affiliation: Universität Siegen , D-57072 Siegen, Germany.
authors.forename: Volkan
authors.initials: V
authors.lastname: Kilic
authors.affiliation: ESRF , F-38000 Grenoble, France.
authors.forename: Roberto
authors.initials: R
authors.lastname: Felici
authors.affiliation: Vienna University of Technology , Institute of Chemical Technologies and Analytics, Getreidemarkt 9, A-1060 Vienna, Austria.
authors.forename: Tobias M
authors.initials: TM
authors.lastname: Huber
authors.affiliation: Vienna University of Technology , Institute of Chemical Technologies and Analytics, Getreidemarkt 9, A-1060 Vienna, Austria.
authors.forename: Edvinas
authors.initials: E
authors.lastname: Navickas
authors.affiliation: Vienna University of Technology , Institute of Chemical Technologies and Analytics, Getreidemarkt 9, A-1060 Vienna, Austria.
authors.forename: Ghislain M
authors.initials: GM
authors.lastname: Rupp
authors.affiliation: Vienna University of Technology , Institute of Chemical Technologies and Analytics, Getreidemarkt 9, A-1060 Vienna, Austria.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Fleig
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany; Fachbereich Physik, Universität Hamburg, Jungiusstr. 9, 20355 Hamburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Stierle