Efficient Dynamic Piezo‐Photocatalysis of Freestanding Single‐Crystal BaTiO 3 Membranes by Strain Gradient

ABSTRACT Piezocatalysis, capable of direct mechanical‐to‐chemical energy conversion, emerges as a promising strategy to address the global challenge of antibiotic pollution. Herein, freestanding single‐crystal BaTiO 3 membranes featuring superior piezo‐photocatalytic activity are fabricated via a water‐soluble sacrificial layer‐assisted pulsed laser deposition process. Ultrasonic cavitation‐induced strain gradients trigger dynamic a/c domain switching, which suppresses the screening effect and enhances the built‐in electric field, enabling dynamic tuning of piezoelectric polarization and sustained carrier separation. Surpassing its substrate‐clamped counterpart, the freestanding membrane exhibits a degradation activity 1.88 times higher under ultrasound. Under piezo‐photocatalytic synergy, it achieves a tetracycline removal efficiency of 90.25%, demonstrating superior broad‐spectrum degradability. This study establishes freestanding single‐crystal membranes as a transformative paradigm material form in piezocatalysis by decoding the cross‐scale coupling mechanism linking macroscopic strain gradients, microscopic domain evolution, and nanoscopic carrier dynamics, thereby paving a novel avenue for designing high‐performance catalysts.