Sm <sub>0.5</sub> Sr <sub>0.5</sub> CoO <sub> 3− <i>δ</i> </sub> Surface Modification of La <sub>0.6</sub> Sr <sub>0.4</sub> Co <sub>0.2</sub> Fe <sub>0.8</sub> O <sub> 3− <i>δ</i> </sub> -Ce <sub>0.9</sub> Gd0.1 <sub> 2− <i>δ</i> </sub> Composite Oxygen Electrodes for Solid Oxide Electrochemical Cells
Matthew Y. Lu, Tianrang Yang, Roberto Scipioni, Yvonne Chart, Alexander Furlong, Scott A. Barnett
Abstract
La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3− δ -Ce 0.9 Gd 0.1 O 2− 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 Sm 0.5 Sr 0.5 CoO 3− 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.