Enhanced stability of electrocatalytic properties against cathodic current polarization for chromium ferrite perovskite-based composite cathodes

Abstract

The structure, electrical conductivity, thermal expansion and electrocatalytic activity of (100-x) vol% La0.3Sr0.7Fe0.7Cr0.3O3-δ-x vol% Ce0.8Sm0.2O1.9 (x = 10–50) composites were investigated in comparison with single-phase La0.3Sr0.7Fe0.7Cr0.3O3-δ perovskite. The Ce0.8Sm0.2O1.9 component in the composites served to repress the formation of oxygen vacancies on the surface and in the bulk of the La0.3Sr0.7Fe0.7Cr0.3O3-δ component at elevated temperatures, which affected the electrical conductivity, thermal expansion and electrocatalytic activity for oxygen reduction reaction as a result. Moreover, the introduction of Ce0.8Sm0.2O1.9 into La0.3Sr0.7Fe0.7Cr0.3O3-δ resulted in a catalytic spillover effect beneficial to the electrocatalytic activity of the composites. The optimal composition of the composites was determined to be x = 30 based on an overall evaluation of various properties. A porous electrode of the composite with x = 30 achieved a polarization resistance of 0.074 Ω·cm2 at 800 °C in air. In sharp contrast to a porous electrode of La0.3Sr0.7Fe0.7Cr0.3O3-δ, the composite electrode showed appreciably alleviated surface strontium segregation and substantially minimized electrode deactivation after exposure to cathodic current polarization. The enhanced stability of the electrocatalytic activity of the composite electrode against cathodic current polarization was explained with respect to the repression and catalytic spillover effects induced by the Ce0.8Sm0.2O1.9 component.