Abstract
In this work the electrochemical oxygen exchange reaction on the system platinum/yttria stabilized zirconia (YSZ) was investigated by means of impedance spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS) on well-defined dense platinum thin film electrodes. From impedance measurements on differently sized electrodes it was possible to show that the resistance caused by the rate determining step scales with the inverse length of the three phase boundary (TPB). To reveal information on the properties of the electrochemically active zone - i.e. the zone where oxygen is incorporated into the electrolyte - 18O tracer experiments combined with ToF-SIMS analysis were carried out. The extension of the active zone was found to depend on the overpotential η. In addition, the ToF-SIMS investigations revealed an enrichment of impurities in the vicinity of the TPB after dc load. The influence of sample pretreatment on the electrode performance is discussed.