Transient and permanent effects of direct current on oxygen transfer across YSZ-Electrode interfaces

The impedance response of a Pt/YSZ (yttria-stabilized zirconia) interface at 900 degrees C is modified by the passage of direct currents. The initial steady-state impedance spectra are different from those taken after current interruption. The latter evolve toward a new steady state. The magnitude and equilibration kinetics of this effect are complex functions of the direction and magnitude of the applied current and the history of gas exposure. An equivalent circuit that models the evolving changes in the impedance spectra is proposed. The analysis of the effect may provide an insight into the mechanism of the anodic and cathodic interfacial reactions in a solid oxide fuel cell.