Operando X-ray Investigation of Electrode/Electrolyte Interfaces in Model Solid Oxide Fuel Cells

Sergey Volkov (1, 2) , Vedran Vonk (1) , Navid Khorshidi (3) , Dirk Franz (1, 2) , Markus Kubicek (4) , Volkan Kilic (5) , Roberto Felici (6) , Tobias M. Huber (4) , Edvinas Navickas (4) , Ghislain M. Rupp (4) , Juergen Fleig (4) , Andreas Stierle (1, 2)

1 DESY - Deutsches Elektronen-Synchrotron [Hamburg]
2 Univ Hamburg, Fachbereich Phys, Jungiusstr 9, D-20355 Hamburg, Germany
3 Max Planck Institute for Intelligent Systems [Tübingen]
4 Vienna Univ Technol, Inst Chem Technol & Analyt, Getreidemarkt 9, A-1060 Vienna, Austria
5 Univ Siegen, D-57072 Siegen, Germany
6 ESRF - European Synchrotron Radiation Facility

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-delta (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 as 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

Domaines: Chimie

Sergey Volkov, Vedran Vonk, Navid Khorshidi, Dirk Franz, Markus Kubicek, et al.. Operando X-ray Investigation of Electrode/Electrolyte Interfaces in Model Solid Oxide Fuel Cells. Chemistry of Materials, 2016, 28 (11), pp.3727-3733. ⟨10.1021/acs.chemmater.6b00351⟩. ⟨hal-01572741⟩