Structure-tailored superlattice Bi₇Ti₄NbO₂₁: Coupling octahedral tilting and rotation induced high ferroelectric polarization for efficient piezo-photocatalytic CO₂ reduction

Intergrowth ferroelectric semiconductors with excellent spontaneous polarization field are highly promising piezo-photocatalytic candidate materials. In addition, developing structural design and revealing polarization enhancement in-depth mechanism are top priorities. Herein, we introduce the intergrowth ferroelectrics Bi₇Ti₄NbO₂₁ thin-layer nanosheets for piezo-photocatalytic CO₂ reduction. Density functional theory (DFT) calculations indicate that interlayer lattice mismatch leads to increased tilting and rotation angle of Ti/NbO₆ octahedra on perovskite-like layers, serving as the main reason for increased polarization. Furthermore, the tilting and rotation angle of the interlayer octahedron further increase under stress, suggesting a stronger driving force generated to facilitate charge carrier separation efficiency. Meanwhile, Bi₇Ti₄NbO₂₁ nanosheets provide abundant active sites to effectively adsorb CO₂ and acquire sensitive stress response, thereby presenting synergistically advanced piezo-photocatalytic CO₂ reduction activity with a high CO generation rate of 426.97 ​μmol ​g⁻¹ ​h⁻¹. Our work offers new perspectives and directions for initiating and investigating the mechanisms of high-performance intergrowth piezo-photocatalysts.