Unraveling synergistic effect of ferroelectric polarization and Z-scheme heterostructure for exceptional piezo-photocatalytic water splitting

Solar-driven photocatalytic water splitting represents an attractive pathway for green hydrogen generation. Nonetheless, the overall efficacy of this approach is often hampered by rapid charge recombination and insufficient reactive sites. Herein, we constructed a covalently linked Z-scheme heterostructure by integrating COF-TpDb with ferroelectric BaTiO 3 nanorods. The optimized COF-TpDb@BTO heterostructure achieves a remarkable piezo-photocatalytic H 2 evolution rate of 10.4 mmol g −1 h −1 under concurrent light and ultrasonic vibration, surpassing most reported covalent organic framework-based and piezoelectric-based photocatalytic systems. Through combined piezoresponse force microscopy and Kelvin probe force microscopy, it directly validates that the switchable piezoelectric polarization and the resultant built-in electric field drive the directional migration of photogenerated charge carriers, thereby suppressing their recombination. The synergy between piezoelectric polarization and interface engineering is evidenced by a strong preserved piezoresponse and a significant 24% boost in the H 2 evolution rate when the sample is treated by corona poling. Furthermore, density functional theory calculations reveal that the hydrogen evolution reaction energy barrier reduces from 0.14 eV to 0.04 eV with the piezoelectric effect. The electrons at the interface are inclined to diffuse from BTO toward COF-TpDb, thus accelerating the electron-hole separation efficiency. This work provides insights into the underlying mechanism of the synergy between piezoelectric polarization and interface engineering in piezo-photocatalytic systems.