A Comprehensive Understanding of Cathodic and Anodic Polarization Effects on Stability of Nanoscale Oxygen-Electrode for Reversible Solid Oxide Cells.

Degradation of oxygen-electrode in reversible solid oxide cells operating in both electrolysis and fuel-cell modes is critical issue that should be tackled. However, origins and mechanisms thereof have been diversely suggested mainly due to a difficulty in precise analysis of microstructural/compositional changes of porous electrode, which is a typical form in solid oxide cells. In this study, we investigate the degradation phenomena of oxygen-electrode under electrolysis and fuel-cell operations, respectively, using a geometrically well-defined, nanoscale LaSrCoFeO (LSCF) dense film with a thickness of ~ 70 nm. Based on assessments of electrochemical properties and analyses of microstructural and compositional changes after long-term operations, we suggest consolidated degradation mechanisms of oxygen-electrode, including the phenomena of kinetic demixing/decomposition of LSCF, which is not readily observable in the typical porous-structured electrode.