The activation energy of the oxygen evolution/oxygen reduction process at perovskite type oxygen electrode materials is slightly higher than that of oxygen transport in the classical electrolyte materials, and also of that of the steam-splitting/hydrogen oxidation process at the fuel electrode. Today at 750 oC – 800 oC state of the art oxygen electrodes do not limit overall SOEC/SOFC performance, but when pushing the operation temperature lower, towards 600 oC the oxygen electrode can become limiting. Hence, there is still a need to develop high performing and importantly, durable, oxygen electrodes.One mechanism that has been reported to reduce oxygen exchange rates at Sr-containing perovskite type electrode materials is Sr segregation to the surface. This has especially been studied and observed on model systems like thin films [1, 2] and bulk materials [3, 4]. A surface enrichment in Sr will potentially make an electrode more vulnerable to degradation by reaction with gas-phase impurities like CO2 and Sulphur-species, but also to Cr-poisoning. Hence, it is important to study what drives such surface enrichment and how to mitigate its consequences.We have studied this in some detail on La0.6Sr0.4FeO3 both on thin films [2] and on bulk samples [4]. Interestingly, on the thin film model system, one can to some extent alleviate the consequences of the enrichment by leaching away excess Sr [1,2]. On the bulk samples, we have found that the oxygen exchange kinetics decrease with aging at low temperature (650 oC), but that the samples can be rejuvenated by a short high temperature treatment [4].In this contribution, we shall present the relation between the oxygen exchange rates measured on La0.6Sr0.4FeO3 surfaces and the chemistry of the surface. It turns out, that Sr enrichment to the surface occurs very fast and the “rejuvenation” treatment does not affect the Sr content at the surface, but rather in which phase/environment the Sr is found.We shall further discuss the implications of the learnings on above presented model-type-systems to the technical level, where often the materials are applied in form of composites.[1] Z. Cai, M. Kubicek, J. Fleig and B. Yildiz, Chem. Mater., 2012, 24, 1116–1127[2] Tripković, D., Küngas, R., Mogensen, M. B. & Hendriksen, P. V., 2020, Physical Chemistry Chemical Physics. 22, 27, p. 15418-15426[3] Edith Bucher, Werner Sitte, Solid State Ionics 192 (2011) 480–482.[4] Đ. Tripković, R. Küngas, M. B. Mogensen and P. V. Hendriksen, J. Mater. Chem. A, 2019, 7, 11782–11791. Figure 1