Zirconia Overcoats and Ceria Nanoparticles Do Not Improve the 650oC Stability of LSCF-Infiltrated Solid Oxide Cell Electrodes More When Used Together

Abstract

Previously, porous 1-5 nm thick atomic layer deposited (ALD) zirconia overcoats or pre-infiltrated gadolinium doped ceria (GDC) nanoparticles were shown to independently improve La0.6Sr0.4Co0.8Fe0.2O3-x (LSCF)-infiltrated Solid Oxide Cell (SOC) oxygen electrode stability (without deteriorating initial performance) by chemically gettering interfacial Sr from the LSCF interfaces. Unfortunately, the experiments here showed that the deposition of porous 1-5 nm thick ALD zirconia overcoats on GDC-pre-infiltrated LSCF-GDC electrodes did not lead to larger-than-previously-achieved improvements in the initial 650oC polarization resistance (RP ) or open-circuit 1000-hour 650oC RP degradation rate. Electrochemical Impedance Spectroscopy (EIS) modeling indicated that in all cases the observed degradation was consistent with increased oxygen exchange resistance at the LSFC-GDC and LSCF-air interfaces caused by enhanced Sr segregation, while Scanning Electron Microscopy (SEM) results showed that the observed degradation was not the result of infiltrate particle coarsening. X-ray Photoelectron Spectroscopy also suggested that in zirconia overcoated GDC pre-infiltrated cells, Sr was mainly gettered by zirconia overcoats that may have been compromised by the pre-infiltrated GDC.