Weak Force-Polarization-Driven Excellent Piezo-PEC Water Splitting by Coupling Dual-Active Piezoelectric Semiconductor with Defect Engineering in BiVO₄/Bi₂MoO₆ Heterojunction

BiVO4 (BVO) is a typical bismuth-based photocatalyst widely utilized across various fields. Nonetheless, its visible light catalytic activity remains constrained by several challenges, including limited light responsiveness and low charge separation efficiency. In this study, we developed a simple method based on the BiVO4/Bi2MoO6 heterojunction to effectively address these issues. This is the first instance of introducing artificial O-vacancies (OVs) into Bi2MoO6 (BMO), in combination with a piezoelectric polarized electric field. Under ultrasonic conditions, the photocurrent density of Ovs BVO/BMO reached 0.34 mA/cm2 at 1.23 VRHE (6.3 times that of naked BVO). The data show that the combination of BVO and BMO improves the photoresponse range of the photoelectrode and the special migration path formed accelerates the separation of photogenerated charge. Due to the excellent piezoelectricity of the two, the recombination of photogenerated charge is significantly inhibited after the introduction of an internal electric field. OVs provide an intermediate level in the band gap, thereby aiding in charge transfer and separation processes. When subjected to ultrasonic waves, they are more prone to becoming stress points, thereby stimulating the piezoelectric polarization of the sample. This work provides a reference for improving the performance of piezoelectric-photoelectric catalysis (piezo-PEC) based on heterojunctions and provides an optimization idea for the field of piezo-PEC.