Electronic Structure Measurements of Heteroepitaxial Solid Oxide Fuel Cell Cathode Thin Films

Synchrotron based hard x-ray photoelectron spectroscopy (HAXPES) technique has been utilized to measure the oxidation states of the associated ions on the surface of strontium doped lanthanum cobalt iron oxide (LSCF), as a function of strontium dopant concentration and gas composition. LSCF is a widely used cathode material for solid oxide fuel cells (SOFCs), which are ideally suitable for environmentally benign electricity generation. However, LSCF suffers from long term stability issues by surface segregation phenomena under typical SOFC working conditions. Leveraging the capability of HAXPES to overcome surface contamination issues and obtaining information from tunable penetration depth, depth dependence information about changes in the electronic structure were obtained, which helps better understand the segregation phenomena. Surface chemistry of both as-deposited and post-annealed LSCF thin films with different Sr concentrations are discussed.