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/PbTiO3 p-n heterojunction has been built up by a facile precipitation–deposition method. The synergistic interaction between p-BiOI and n-PbTiO3 with abundant oxygen vacancies was confirmed by HRTEM and XPS analyses. Enrichment of oxygen vacancies in the BiOI/PbTiO3 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/PbTiO3 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 PbTiO3, resulting in an effective decrement of the charge recombination process, as confirmed by PL, EIS, photocurrent, and Bode analyses.