Effect of Atomic Layer Deposition of Ultra‐Thin Oxide on Reactivity and Durability of Perovskite Oxygen Electrodes

ABSTRACT Conductive perovskite oxides (ABO 3 ) are key oxygen electrode materials for energy conversion applications, but they suffer from irreversible performance degradation at elevated temperatures due to surface chemical instability. In this study, we investigate how the surface chemical environment and oxygen exchange kinetics of thin‐film La 0.6 Sr 0.4 CoO 3 are affected by the atomic layer deposition of binary oxides—specifically HfO 2 and Al 2 O 3 . We observe that both HfO 2 and Al 2 O 3 overcoats successfully maintain the rapid oxygen exchange rate on the electrode surface. Interestingly, however, their effects on the electrode surface chemistry differ significantly, as do the ideal coating thicknesses, as revealed by X‐ray photoelectron spectroscopy, secondary ion mass spectrometry, and transmission electron microscopy analyses. These findings suggest two distinct mechanisms for stabilizing the perovskite surface: the oxide overcoats (1) reduce oxygen vacancies that attract Sr ions to the surface and (2) act as a scavenger, consuming excess surface Sr, and suggest the design principle of a new strategy based on atomic layer deposition to improve perovskite surface durability.