Engineering of Charged Defects at Perovskite Oxide Surfaces for Exceptionally Stable Solid Oxide Fuel Cell Electrodes.

Cation segregation, particularly Sr segregation, toward a perovskite surface has a significant effect on the performance degradation of a solid oxide cell (solid oxide electrolysis/fuel cell). Among the number of key reasons generating the instability of perovskite oxide, surface-accumulated positively charged defects (oxygen vacancy, V) have been considered as the most crucial drivers in strongly attracting negatively charged defects (Sr) toward the surface. Herein, we demonstrate the effects of a heterointerface on the redistribution of both positively and negatively charged defects for a reduction of V at a perovskite surface. We took SmSrCoO (SSC) as a model perovskite film and coated GdCeO (GDC) additionally onto the SSC film to create a heterointerface (GDC/SSC), resulting in an ∼11-fold reduction in a degradation rate of ∼8% at 650 °C and ∼10-fold higher surface exchange () than a bare SSC film after 150 h at 650 °C. Using X-ray photoelectron spectroscopy and electron energy loss spectroscopy, we revealed a decrease in positively charged defects of V and transferred electrons in an SSC film at the GDC/SSC heterointerface, resulting in a suppression of negatively charged Sr (Sr) segregation. Finally, the energetic behavior, including the charge transfer phenomenon, O p-band center, and oxygen vacancy formation energy calculated using the density functional theory, verified the effects of the heterointerface on the redistribution of the charged defects, resulting in a remarkable impact on the stability of perovskite oxide at elevated temperatures.