Dipole Moment and Built-In Polarization Electric Field Induced by Oxygen Vacancies in BiOX for Boosting Piezoelectric–Photocatalytic Removal of Uranium(VI)

Piezoelectric–photocatalysis is distinguished by its piezoelectricity as an external force that induces deformation within the catalyst to engender a polarized electric field compared to conventional photocatalysis. Herein, the piezoelectric photocatalyst BiOBr has been expertly synthesized via a plasma process and applied for piezoelectric–photocatalysis removal of uranium(VI) for the first time. The abundant surface oxygen vacancies (OVs) could induce a dipole moment and built-in electric field, which endows BiOBr with excellent separation and transport efficiency of photogenerated charges to actuate more charges to participate in the piezoelectric–photocatalytic reduction process. Consequently, under visible light and ultrasound (150 W and 40 kHz), the removal rate constant of OVs-BiOBr-30 (0.0306 min –1 ) was 2.4, 30.6, and 6 times higher than those of BiOBr (0.01273 min –1 ), ultrasound, or photocatalysis, respectively. The piezoelectric–photocatalytic synergy is also universal for BiOX (X = Cl, Br, or I) to accelerate the reduction rate of uranium(VI). This work highlights the role of piezoelectric–photocatalysis in the treatment of uranium-containing wastewater, which is of great significance for resource conservation and environmental remediation.