Self-Aligned BiFeO ₃ Polarization Vector Induced by MnO ₆ Octahedral Jahn–Teller Distortion for Enhanced Photocatalytic CO ₂ Reduction

Precise modulation of polarization vector alignment through chemical synthesis strategies remains challenging for designing high-performance ferroelectric photocatalysts. Herein, the proposed Jahn-Teller distortion-mediated mechanism resolves the polarization disorder by elongating MnO₆ octahedra to drive the coordinated displacement of neighboring atoms along a uniform direction without an external electric field. Specifically, the localized charge of Mn is modulated via redistribution with oxygen ligands, thereby achieving an optimal electronic configuration (Mn t_2g³e_g¹) that induces a maximal Jahn-Teller distortion, as confirmed by X-ray absorption and Raman spectroscopies. Notably, atomic pair distribution functions demonstrate that the structural evolution of the Jahn-Teller unit directly propels displacement of Fe and O atoms along the [001̅] crystallographic direction, which intensifies the asymmetric deformation of FeO₆ octahedra, forming an oriented polarization. Consequently, the rapid separation of carriers driven by the depolarization electric field motivates the conversion from CO₂ to CO with a yield of 30.51 μmol g^-1 h^-1 under pure water conditions, which is almost five times that of the original BiFeO₃. This study proposes an innovative strategy to modulate the polarization vector via Jahn-Teller distortion, offering insights into the development of ferroelectric photocatalysts from the perspective of the electronic structure.