Oxygen reduction via grain boundary transport in thin film platinum electrodes on yttria stabilized zirconia

AbstractModel-type sputter deposited platinum microelectrodes with different grain sizes were investigated on single crystalline yttria stabilized zirconia (YSZ) by means of impedance spectroscopy. Measurements on single platinum microelectrodes could be continuously performed for >100h and from 250 to 800°C without losing contact. From the temperature dependence, two parallel reaction pathways for oxygen reduction could be identified. Above 450°C, a surface path with a rate determining step located at the three phase boundary is predominant. Its polarization resistance is independent of the Pt grain size and exhibits an activation energy of ca. 1.8eV. In the low temperature regime (