Achieving Fast Reconstruction of Metal/Ruddlesden‐Popper Layered Perovskite Heterointerfaces via Structural Flexibility‐Driven Phase Transition Engineering for Efficient and Durable CO ₂ Electrolysis

Abstract In situ constructing active metal/oxide interfaces has extensive applications for CO ₂ electrolysis in solid oxide electrolysis cells (SOECs) but faces critical challenges due to sluggish diffusion process of B‐site cations inside the perovskite bulk. Herein, the diffusion kinetics of Fe and Ni cations in Sr _0.9 Ti _0.45 Fe _0.5 Ni _0.09 O _3‐δ (S _0.9 TFN _0.09 ) are greatly facilitated via structural flexibility. The synergistic modification of Sr‐site defects and excess Ni incorporation enables flexible coordination and enhanced intrinsic oxygen properties, driving a bulk‐surface reconstruction under reducing condition. As a consequence, the heterostructured FeNi alloy (FNA) and metallic Fe nanoparticles are readily in situ exsolved onto Ruddlesden‐Popper layered perovskite (RP‐STF) surface. The phase transition process significantly increases the number of exsolved particles. Compared with pristine matrix, the reconstructed FNA/Fe@RP‐STF interfaces deliver markedly enhanced electrocatalytic activity for CO ₂ adsorption and dissociation, thus reach a 51% improvement in CO ₂ electrolysis performance at 1.5 V and 800 °C. Moreover, the operating stability and anticoke properties are enhanced due to strongly interactive heterointerfaces. This work provides a sufficiently simple strategy to rapidly achieve microstructural evolution for CO ₂ electrolysis and other energy conversion.