Regulating carrier transport in dual Z-scheme heterojunction KNbO3/MoSe2/Zn2In2S5 by dual piezoelectric polarization electric field

Reasonable design of heterojunction is a rational way to boost charge separation and piezo-photocatalytic performance of semiconductors. Herein, a dual Z-scheme KNbO₃/MoSe₂/Zn₂In₂S₅ (KMZIS) heterojunction was synthesized, in which KNbO₃ and MoSe₂ provide piezoelectricity, and Zn₂In₂S₅ offers photoactivity. UV–Vis DRS, Mott–Schottky plots, and DFT calculations confirmed the existence of two co-directional built-in electric fields, which respectively enhanced the accumulation of photogenerated electrons and holes on the conduction band of Zn₂In₂S₅ and the valence band of KNbO₃, respectively, enabling the heterojunction to exhibit stronger redox capabilities under illumination. Under mechanical vibration, the maximum piezoelectric current density of KMZIS-25 can reach up to 26.7 µA /cm², which is 1.7 and 2.6 times higher than that of KNbO₃/MoSe₂ and MoSe₂/Zn₂In₂S₅, respectively. Under the synergistic piezoelectric–photoelectric coupling effect, KMZIS-25 exhibits a TCH degradation rate constant of 60.53 × 10^-2 min⁻¹, a H₂O₂ yield of 64.70 mmol·h⁻¹·g⁻¹, and a H₂ evolution rate of 37.12 mmol·h⁻¹·g⁻¹, which are 4.6, 4.4, and 4.1 times higher than photocatalysis alone, and 3.8, 3.1, and 2.7 times higher than piezocatalysis alone. This indicates that the bi-piezoelectric field synergistically accelerates charge transfer in KMZIS, thereby significantly improving the catalytic performance of heterojunction.