Interlayer Slip Engineering Induces Unexpected Out‐Of‐Plane Piezoelectricity in Group‐VA Nanosheets

ABSTRACT Piezoelectricity, arising from inversion symmetry breaking, is generally forbidden in centrosymmetric β‐phase bismuth (Bi) and antimony (Sb) structures. Here, we experimentally demonstrate a previously unreported out‐of‐plane piezoelectricity in β‐phase Bi and Sb nanosheets synthesized via electrochemical exfoliation. Piezoresponse force microscopy (PFM) and second‐harmonic generation (SHG) measurements confirm the strong piezoelectric response with a longitudinal coefficient (d ₃₃ ) up to ∼200 pm V ⁻¹ , comparable to or exceeding that of conventional 2D piezoelectric materials. Density functional theory (DFT) calculations reveal that interlayer slip during exfoliation induces a transition from AA‐ to AB‐stacking, effectively breaking inversion symmetry and leading to large out‐of‐plane polarization. This discovery introduces a universal mechanism to generate piezoelectricity in non‐piezoelectric 2D materials through stacking‐mode engineering, providing opportunities for nanoscale electromechanical and piezocatalytic devices.