Dynamic Active Site Mechanism and Compositional Tuning in La x Sr 1−x Co y Fe 1−y O ₃ (LSCF) Perovskites Toward Efficient Oxygen Evolution

The oxygen evolution reaction is widely recognized as the kinetic bottleneck in water electrolysis, mainly because strong oxygen bonding and sluggish multi‐electron transfer slow down the reaction. Transition metal oxides are promising catalysts for this step, and their activity is interpreted with either the adsorbate evolution mechanism (AEM) or the lattice oxygen mechanism (LOM). However, these interpretations overlook essential dynamic features of oxide surfaces. In particular, the conventional AEM assumes fixed metal‐centered active sites, whereas the LOM depends on forming oxygen vacancies that are energetically inaccessible in many stable oxides. As a result, neither framework reliably captures the reactivity of robust perovskites. To address this limitation, we investigated La x Sr 1−x Co y Fe 1−y O 3 (LSCF), a widely used yet mechanistically unresolved perovskite system. Therefore, we developed a dynamic active site mechanism in which adsorbed O migrates from a metal site to a nearby lattice oxygen site. Within this framework, dynamic O migration lowers reaction free energies relative to the conventional pathway and shows that an optimal La to Sr ratio near 0.6 governs intrinsic activity, with Co providing additional gains. Furthermore, electronic structure analysis shows that a moderate O 2 p ‐band level and balanced structural rigidity jointly promote this dynamic behavior. Taken together, these findings indicate that a dynamic active site mechanism operates in LSCF and offer guidance for composition tuning to support the design of durable cost‐effective oxide electrocatalysts for water splitting.