Structural, Interfacial, and Electrochemical Stability of La0.3Ca0.7Fe0.7Cr0.3O3-δ Electrode Material for Application as the Oxygen Electrode in Reversible Solid Oxide Cells

Abstract

A detailed study aimed at understanding the structural, interfacial, and electrochemical performance stability of La0.3Ca0.7Fe0.7Cr0.3O3-δ (LCFCr) electrode material for application as the oxygen electrode in reversible solid oxide cells (RSOCs) is presented. Specifically, emphasis is placed on the stability of the LCFCr oxygen electrode during oxygen evolution (electrolysis mode), whereby many known electrode materials are known to fail due to delamination. The porous microstructure of the electrode was characterized by nanoscale X-ray microscopy (XRM) to reveal the percentage porosity, pore connectivity, average pore size, and electrochemical surface area, etc. Under polarization in a two-electrode symmetrical-cell configuration, while the working electrode was under anodic polarization, a very stable performance was observed at a cell potential of 0.2 V, although increasing the cell potential to 0.65 V caused significant performance degradation. This degradation was reversible when the cell was run at open circuit for 10 h. High-resolution transmission electron microscopy and wavelength dispersive spectroscopy revealed that the working electrode (LCFCr)/electrolyte (GDC) interface was structurally and chemically stable after hundreds of hours under polarization with no interdiffusion of the various species observed across the interface, hence rendering LCFCr a viable alternative for the oxygen electrode in RSOCs.