Interfacial effect on the polarization resistance of SrM0.1Mo0.9O3-? (M=Mg2+, Fe3+)/GDC-based composite electrodes

The present study examines the interfacial effect on the area-specific resistance (ASR) offered by SrM0.1Mo0.9O3-delta (M = Mg2+, Fe3+)/Gd0.1Ce0.9O2-delta (GDC) composite electrodes. The symmetrical cells having 8YSZ electrolyte and SrFe0.1Mo0.9O3-delta/Gd0.1Ce0.9O2-delta composite electrodes are fabricated with and without the GDC buffer layer. The electrode ASR in cells with and without GDC-buffer layer is 0.09 O.cm2 and 0.68 O.cm2 at 850 degrees C in 3% H2O/H2, respectively. More than a 50% rise in the magnitude of electrode ASR is seen in cells with no GDC buffer layer after 10 redox cycles. Phase analysis of these cells reveals a dense layer of an insulating SrZrO3-based phase formed at the electrode/electrolyte interface due to the chemical reaction between SrFe0.1Mo0.9O3-delta and 8YSZ. In contrast, the cells possessing a GDC buffer layer show a small ASR increase from 0.09 O.cm2 to 0.14 O.cm2 after the same number of redox cycles without the presence of any secondary phase. The effect of the current collector contact area on the ASR of the SrMg0.1Mo0.9O3-delta/Gd0.1Ce0.9O2-delta composite electrode is also evaluated. Symmetrical cells with a dense GDC buffer layer and composite electrodes are prepared. The Pt current collector area on the electrode layer is varied from 0.13 cm2 to 0.5 cm2, and the electrode specific resistance is measured at 850 degrees C in a 3% H2O/H2 environment. The electrode resistance declines with increasing current collector area. The cell with the electrode surface entirely covered by the current collector exhibits a very low ASR of - 0.07 O. cm2. The sensitivity of the interfacial polarization resistance towards a slight change in the strength of the current field is the possible reason for observing such ASR variation.