Oxygen transport paths in screen-printed Pt-Al2O3 composite model electrodes on YSZ

In this work, Pt-Al2O3 composite electrodes without open porosity, screen-printed on polycrystalline YSZ, were analysed in order to identify relevant oxygen transport paths in thick-film electrodes. By using electrochemical impedance spectroscopy, the electrode processes were investigated at different oxygen partial pressures (pO2) and temperatures (T). Special sample layouts allowed the separation of three phase boundary (tpb) and electrode area-dependent transport processes. We found that the area-related transport path is dominating at low temperatures and high pO2, with a relatively low activation energy of 0.2 to 0.6 eV and a pO2− 0.7 dependence. In contrast, the tpb-related transport path dominates at high temperatures and low pO2, with activation energies between 0.8 and 1.4 eV and a pO2− 0.3 behaviour. A tracer experiment was performed additionally to visualize the location of oxygen incorporation below the electrode.