Enhanced charge carrier separation by bi-piezoelectric effects based on pine needle-like BaTiO3/ZnO continuous nanofibers

Abstract

The separation of photogenerated carriers is particularly important for improving the efficiency of photocatalysis. Using a piezoelectric field or constructing heterojunctions can promote the separation of electron–hole pairs in photocatalysis. However, most of the current catalysts are composites with limited effective interfaces, which results in an enhancement effect that must be further improved. Here, we propose pine needle-like BaTiO₃/ZnO continuous nanofibers with numerous interfaces, which consist of BaTiO₃ nanofibers and ZnO nanorods. They have both photocatalytic and piezoelectric properties, and the one-dimensional shape easily responds to ultrasonic waves and generates a piezoelectric potential, and what's more, the different deformation directions or degrees of BaTiO₃ and ZnO may result in different initial times of piezoelectric potential generation, and the two piezoelectric fields will alternately break the shielding and efficiently separate photogenerated carriers. Under ultrasonic excitation, an interface electric field is formed between BaTiO₃ and ZnO, which increases the rate constant of the piezophotocatalytic reaction by 2.13 times compared to photocatalysis. In particular, compared with pure ZnO and BaTiO₃, the reaction rate constant is increased by 2.15 times and 2.98 times, respectively. Moreover, the difference between the piezophotocatalytic reaction rate constant of BaTiO₃/ZnO and the sum of the piezoelectric and photocatalytic reaction rate constants is significantly higher than that of ZnO and BaTiO₃, showing that the piezoelectric fields generated by ZnO and BaTiO₃ may synergistically promote the separation of photogenerated carriers. This work provides a piezophotocatalyst that can efficiently degrade organic pollutants, which has practical application significance in the field of water treatment.