Robust Cathode for Efficient CO ₂ Electrolysis Driven by FeO ₆ Octahedral Rotation and Jahn–Teller Distortion in Solid Oxide Electrolysis Cells

It is well-established that even minor modulation of the BO 6 octahedra within perovskite structures can induce significant variations in material functionalities, suggesting that controlling the degree of octahedral distortion in perovskite architectures represents a promising approach to further enhance the electrocatalytic performance and stability of perovskite-based electrocatalysts. In this study, a composite perovskite cathode (Sr 2 Fe 1.54 Mo 0.46 O 6−δ +SrMoO 4 ) for solid oxide electrolysis cells was synthesized using a sintering-free self-assembly method. Comprehensive characterizations and density functional theory calculations reveal that the Sr 2 Fe 1.54 Mo 0.46 O 6−δ perovskite undergoes octahedral rotations, and the increase in Fe 4+ ( t 2g 3 eg 1 ) is accompanied by asymmetric electron occupation within degenerate orbitals, inducing Jahn–Teller distortion in FeO 6 octahedra. These octahedral deformations modulate the coordination environment of the Fe-site, with their optimized spatial orientation of orbitals effectively capturing intermediates linked to surface–adsorbate bonds. This enhances metal–oxygen hybridization and shifts the O 2p band center toward the Fermi level, facilitating oxygen vacancy formation and improving the CO 2 adsorption capability. Consequently, these features enable a current density of 1.58 A cm –2 at 800 °C and 1.5 V, significantly outperforming the idealized Sr 2 Fe 1.5 Mo 0.5 O 6−δ -based system (0.87 A cm –2 ) under the same conditions. This work elucidates the influence of FeO 6 octahedral distortion on high-temperature CO 2 reduction reaction performance and its underlying mechanisms and proposes a straightforward method for the design of solid oxide cell electrocatalysts.