Platinum Migration at the Pt/YSZ Interface

Electrode activation, inductive hysteresis and non-linearity are well known phenomena on Pt-YSZ electrodes, and recently also regular fluctuation patterns have been reported. The oxygen electrode on YSZ surfaces is studied at Pt micro-electrodes prepared by electrochemical etching of platinum wire. The result is a well defined contact area of ~20 µm in diameter. Due to the small size and a favourable ratio between the three phase boundary (TPB) length and the contact area, micro-electrodes should have an increased sensitivity to discrete events at the TPB. The electrode processes are studied by potential sweep, step and impedance techniques. As expected, inductive behaviour and activation during step polarization is confirmed, but furthermore, a very accentuated noise pattern is seen during cathodic step polarization. Investigation of the YSZ and Pt surfaces afterwards reveals the growth of dendrite like Pt structures from the TPB. The formation of these may explain the observed noise and contribute to the explanation of the activation mechanism taking place at the platinum-YSZ interface.