Electrical characterization of the platinum/YSZ interfaces in SOFCs via micro-contact impedance spectroscopy

The concept of micro-contact in electrodes was incorporated into AC two-probe impedance spectroscopy in order to clarify the electrode-related responses in solid oxide fuel cells (SOFCs). The pointed contact of one electrode was combined with the planar electrode as a counterpart in characterizing an YSZ (yttria-stabilized zirconia)/Pt interface of SOFCs. The micro-contact in electrodes induced the decrease in capacitance and the increase in impedance and amplified the bulk responses in YSZ due to the constricted electroding area. The bulk-related portions can be separated from the interfacial polarization of Pt, even though the electrolyte/electrode interface was found to be very sensitive to the measurement condition, i.e., the oscillating voltage. The resolved bulk and interfacial resistances were analyzed using a concept of “spreading resistance.’’ Furthermore, the electrode-related issues were ramified for the application of impedance spectroscopy to the solid oxide fuel cells.