Structural Stability and Catalytic Activity of Lanthanum-Based Perovskites

Perovskite-type oxide materials with a general formula La(1-x)A(x)Fe(1-y) Co(y)O(3-delta), where A is an alkaline earth metal Sr or Ba, have been studied as cathode materials for catalytic reduction of oxygen in solid oxide fuel cells (SOFCs), as well as combustion catalysts. In this study, we use a combination of temperature-programmed reduction measurements, X-ray diffraction, carbon black catalytic oxidation measurements, and first-principles, density-functional-theory (DFT) calculations to elucidate the main processes that contribute to the structural stability and catalytic activity for soot oxidation of these materials. In particular, we investigate the dynamics of the structure reconstruction with oxygen loss during the regulated increase of the temperature. The calculations are in good qualitative agreement with catalytic experiments and allow us to identify special combinations of the perovskite chemical composition and local surface structures for which one could expect the highest catalytic activity for the soot oxidation process.