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Abstract Surface cation segregation, specifically strontium (Sr), has been identified as a primary factor contributing to the performance degradation of perovskite-based oxide electrodes used in various energy conversion devices. However, due to the complex chemistry and structure of the perovskite oxide surfaces, the mechanisms behind Sr segregation and its impact on electrode activity are only partially understood. Moreover, Sr segregation already occurs during perovskite synthesis, further complicating the situation. To address this issue, this study implements a controlled approach using a model thin film system composed of atomically flat SrTi 0.5 Fe 0.5 O 3-δ (STF50) with a stoichiometric surface, enabling detailed examination. The evolution of surface structure, composition, and oxygen exchange kinetics are observed as a function of temperature and time. By integrating experiments and ab initio simulations, we tackle several fundamental questions, including the evaluation of reactivity for pristine perovskite oxide surface before Sr segregation and the correlation between Sr segregation at the surface with oxygen exchange kinetics. Our comprehensive analysis clearly reveals that the decline in performance of the perovskite oxide electrodes is primarily attributed to the detrimental effects of Sr-deficiency on the surface, thereby resolving longstanding debates in the field.
Jung et al. (Mon,) studied this question.
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