Stupendous Photocatalytic Activity of p-BiOI/n-PbTiO₃ Heterojunction: The Significant Role of Oxygen Vacancies and Interface Coupling

The combination of oxygen vacancies and p-n heterojunctions is exploited to pinpoint a valuable opportunity for effective minimization of charge recombination and enhanced photocatalytic activity. Herein, an oxygen-vacancy-rich BiOI/PbTiO 3 p-n heterojunction has been built up by a facile precipitation–deposition method. The synergistic interaction between p-BiOI and n-PbTiO 3 with abundant oxygen vacancies was confirmed by HRTEM and XPS analyses. Enrichment of oxygen vacancies in the BiOI/PbTiO 3 p-n heterojunction was further verified by an ESR test. The effect of combining a p-n heterojunction and oxygen vacancies effectively modulated the physicochemical, electronic, and catalytic properties of the photocatalyst simultaneously. The BiOI/PbTiO 3 p-n heterojunction with rich oxygen vacancies at the optimum concentration showed superior degradation of the antibiotic tetracycline, i.e., 94% in 2 h under solar harvest. The improved activity of the p-n heterojunction is further attributed to the presence of an inner electric field and oxygen vacancies that serve as a new channel for the transformation of photoelectrons from BiOI to PbTiO 3, resulting in an effective decrement of the charge recombination process, as confirmed by PL, EIS, photocurrent, and Bode analyses.