Oxygen Vacancies Promoted Piezoelectricity toward Piezo-Photocatalytic Decomposition of Tetracycline over SrBi₄Ti₄O₁₅

Polarization in noncentrosymmetric materials contributes to the improvement in photocatalytic activity by inhibiting the recombination of photogenerated charge carriers; thus, enhancing polarization becomes an effective way to further improve the photocatalytic efficiency of a photocatalyst. Herein, as a case of study, the piezoelectric coefficient and potential of SrBi4Ti4O15 prepared by a molten salt method (SBT-850) were improved by 4.9 and 2.7 times compared to those of its counterpart prepared by a solid-state reaction (SBT-SSR), respectively. The experimental investigations and theoretical calculations evidence that the oxygen vacancies in the {001}-dominated facets could improve the internal polarization of SBT-850. Piezo- and photocoupled catalysis of SBT-850 is employed to improve the efficiency of photocatalytic degradation and mineralization of tetracycline under the synergy of visible light and ultrasound. The oxidation rate constant under the synergistic stimulation reaches 0.058 min-1, which is 2.15 and 14.5 times higher than that under visible light irradiation or ultrasound only, respectively. Furthermore, the synergistic stimulation promotes the generation of photocatalytic reactive oxygen species, which play an important role in the photocatalytic oxidation of tetracycline. The piezo-photocatalytic decomposition pathway of tetracycline is proposed based on the HPLC-MS analysis and theoretical calculations. This study sheds light on the rational design of oxygen vacancy-based microstructures to enhance the piezo-photocatalytic performance.