Surface Strontium Segregation of Solid Oxide Fuel Cell Cathodes Proved by In Situ Depth-Resolved X-ray Absorption Spectroscopy

Little is known about the structures and chemistry of perovskites, occurring from the surface to the bulk, at high temperatures and ambient oxygen pressures. Changes in the composition and electronic structure of (001)-oriented La0.8Sr0.2CoO3-δ (LSC) films were investigated by using in situ depth-resolved X-ray adsorption (XAS) under practical operating conditions of solid oxide fuel cells. Depth-resolved XAS spectra of LSC films, with a depth resolution of ∼ 2 nm, revealed that the surface regions of ∼10 nm were considerably different from the film bulk. The surface regions were enriched in strontium, which can play an important role in governing the oxygen exchange kinetics at the surface.