Ag surface-coated with nano-YSZ as an alternative to Pt catalyst for low-temperature solid oxide fuel cells

Herein we propose silver surface-coated with nano-scale yttria-stabilized zirconia (YSZ) as a high-performance cathode for use in low-temperature solid oxide fuel cells (LT-SOFCs). YSZ was coated on the Ag cathode surface by sputtering of Y/Zr alloy films followed by thermal annealing for oxidation of YSZ. An electrolyte-support type SOFC was fabricated on 350-μm-thick gadolinium-doped ceria (GDC) pellets. The yttrium concentration and sputtering time for obtaining the YSZ coating layer was varied to optimize the cathode composition. It was determined that the GDC SOFCs with optimized Ag-YSZ cathodes significantly outperform cells with bare silver or platinum cathodes, which are considered to be the best-performing catalysts at low temperatures. The peak power density obtained using cells with Ag-YSZ cathodes was as high as ∼100 mW/cm2 at 450 °C, 3-4 times greater than the performance of cells with Ag or Pt cathodes. Electrochemical impedance spectroscopy was performed during fuel cell testing to compare polarization and charge transport performances of the Ag-YSZ cathodes. The long-term stability of the Ag-YSZ cathode was evaluated by monitoring the change in cathode morphology compared to the bare Ag and Pt cathodes.