Evidence that Surface-Segregated Sr Phases Can Be Removed in LSCF via Ceria Pre-Infiltration, Are Less Apt to Form in SSC

Abstract

Here Ce0.9Gd0.1O1.95−x (GDC) pre-infiltration was performed on 12 vol.% La0.6Sr0.4Co0.8Fe0.2O3−x (LSCF) or Sm0.5Sr0.5CoO3−x (SSC) infiltrated GDC Solid Oxide Fuel Cell cathodes. The addition of 7.5 vol.% of ∼40 nm diameter GDC nanoparticles into a ∼30 μm thick porous scaffold of partially-sintered, sub-micron GDC particles before LSCF infiltration 1) lowered the temperature needed to produce a LSCF-GDC polarization resistance (RP ) of 0.1 Ohm*cm2 by ∼50 °C, and 2) reduced the amount of 500 h, 650 °C open-circuit LSCF-GDC RP degradation from ∼37% to ∼6%. In contrast, GDC pre-infiltration had no effect on the initial SSC-GDC RP or the 19% in RP degradation observed during 500 h of 650 °C open-circuit aging. X-Ray Photoelectron Spectroscopy showed that GDC pre-infiltration lowered the concentration of strontium species on the surface of the initial and 650 °C-aged LSCF-GDC, but had no effect on the initial or aged SSC-GDC Sr concentrations. Similarly, Electrochemical Impedance Spectroscopy showed that for both the initial and aged LSCF-GDC, GDC pre-infiltration improved oxygen exchange at the infiltrate-backbone and infiltrate-gas interfaces, but had no effect on the SSC-GDC. Hence, GDC pre-infiltration was concluded to improve LSCF-GDC performance and durability by scavenging exsolved Sr-rich secondary phases that form on the interfaces of LSCF, but not SSC.