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Oxygen Surface Exchange at Grain Boundaries of Oxide Ion Conductors

Authors

  • Wonyoung Lee,

    Corresponding author
    1. Nanoscale Prototyping Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
    Current affiliation:
    1. Laboratory of Electrochemical Interfaces, Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA, E-mail: leewy@mit.edu
    • Nanoscale Prototyping Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA.
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  • Hee Joon Jung,

    1. Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA
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  • Min Hwan Lee,

    1. Department of Materials Science and Engineering, Seoul National University, Seoul, 151-742, South Korea
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  • Young-Beom Kim,

    1. Nanoscale Prototyping Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
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  • Joong Sun Park,

    1. Nanoscale Prototyping Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
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  • Robert Sinclair,

    1. Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA
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  • Fritz B. Prinz

    1. Nanoscale Prototyping Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
    2. Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA
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Abstract

The role of grain boundaries on oxygen surface exchange in an oxide ion conductor is reported. Atomic-scale characterization of the microstructure and chemical composition near the grain boundaries of gadolinia-doped ceria (GDC) thin films show the segregation of dopants and oxygen vacancies along the grain boundaries using the energy dispersive spectroscopy in scanning transmission electron microscopy (STEM-EDS). Kelvin probe microscopy is employed to verify the charge distribution near grain boundaries and shows that the grain boundary is positively charged, indicating a high concentration of oxygen vacancies. AC impedance spectroscopy on polycrystalline GDC membranes with thin interfacial layers with different grain boundary densities at the cathodes demonstrated that the cells with higher grain boundary density result in lower electrode impedance and higher exchange current density. These experimental evidences clearly show that grain boundaries on the surface provide preferential reaction sites for facilitated oxygen incorporation into the GDC electrolyte.

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