Regulation of Internal Electric Field via d Orbital Occupancy for Efficient CO ₂ Photoreduction

Abstract Developing highly efficient CO ₂ photocatalysts is meaningful; however, the ultrafast recombination of photogenerated electrons and holes severely hinders the photocatalytic reaction. Herein, the internal electric field of ferroelectric KNbO ₃ is further enhanced by optimizing Nb 4d t _{2 g} orbital occupancy states through Nb‐O‐Fe charge transport channels regulated by different doped amounts of Fe as an electron donor, which further improves the separation efficiency of photogenerated electrons and holes. The optimal occupancy state of the Nb 4d t _{2 g} orbital effectively modulates its bonding interactions with neighboring oxygen atoms, achieving the maximum directional displacement of Nb along the [110] polarization axis of the NbO ₆ octahedron at the optimized t _{2 g} orbital occupancy, as evidenced by atomic pair distribution function (PDF) analysis and Raman spectroscopy. The photocatalytic performance revealed that KNbO ₃ with the strongest built‐in electric field exhibited the highest CO yield (15.7 µmol g⁻¹h⁻¹) and selectivity (92.3%). This work paves the way for tuning ferroelectric polarization via orbital regulation and lays a foundation for the rational design of energy‐catalytic ferroelectric structures.