Efficient Dynamic Piezo-Photocatalysis of Freestanding Single-Crystal BaTiO₃ Membranes by Strain Gradient

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 BaTiO₃ 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.