Sm0.5Sr0.5CoO3−δ Surface Modification of La0.6Sr0.4Co0.2Fe0.8O3−δ -Ce0.9Gd0.12−δ Composite Oxygen Electrodes for Solid Oxide Electrochemical Cells

Abstract

La0.6Sr0.4Co0.2Fe0.8O3−δ -Ce0.9Gd0.1O2−δ (LSCF-GDC) composite oxygen electrodes have been widely used in intermediate temperature (<700 °C) solid oxide cells, with composite usually providing better electrochemical performance than single-phase LSCF. However, LSCF-based electrodes are often observed to degrade over time due to Sr segregation. Here we present an impedance spectroscopy study comparing the degradation behaviors of LSCF-GDC and Sm0.5Sr0.5CoO3−δ (SSC) infiltrated LSCF-GDC electrodes. The LSCF-GDC polarization resistance increases by ∼5 times over ∼1000 h at 650 °C. In contrast, the SSC-infiltrated electrode shows similar initial polarization resistance but much more stable performance. The impedance modeling results show that the improved stability is associated with the low frequency oxygen dissociative adsorption/desorption process. The results suggest that this adsorption/desorption process slows due to increased Sr segregation on LSCF over time, and that SSC does not degrade significantly due to Sr surface segregation.