Multi-scale piezoelectric synergy: A porous MoSe₂/BaTiO₃@PVDF membrane for high-efficiency piezo-photocatalysis

High-performance yet recyclable piezo-photocatalysts are highly desired for sustainable energy conversion and environmental remediation but remain constrained by rapid charge recombination and difficult catalyst recovery. Here we embed a dual-piezoelectric MoSe₂/BaTiO₃ (MSe/BT) heterojunction into a porous polyvinylidene fluoride (PVDF) membrane via a freeze-phase-inversion route to construct a hierarchical MoSe₂/BaTiO₃/PVDF (MSe/BT/PVDF) composite. Finite-element simulation and piezoresponse force microscopy reveal that the heterojunction generates a strong interfacial piezoelectric field, while the PVDF matrix undergoes dipole self-polarization, jointly delivering a high longitudinal piezoelectric coefficient (d₃₃ ≈ -114.6 pC N^-1) and accelerating charge separation. Under simultaneous light irradiation and ultrasound, the membrane achieves (i) a hydrogen-evolution rate of 1220.6 μmol h^-1 g^-1 (1.5 × that of MSe/BT powder), (ii) rapid Rhodamine-B degradation with a first-order constant of 0.315 min^-1, and (iii) efficient H₂O₂ production of 6.64 μM min^-1. Electron-spin-resonance and scavenger tests confirm that abundant superoxide (•O₂^-) and hydroxyl (•OH) radicals are produced during piezo-photocatalysis. This multi-scale piezoelectric synergy within a flexible membrane offers a promising approach toward developing recyclable piezo-photocatalysts for green energy and environmental applications.