Effect of phase structure of Bi5O7I on the photocatalytic activity of S-scheme AgBr/Ag/Bi5O7I

The synthesis of pure needle-shaped monoclinic-Bi5O7I (m-Bi5O7I) was reached for the first time at pH 12.2 under a hydrothermal condition, using bismuth citrate as a Bi source. To enhance the photocatalytic activity of m-Bi5O7I, S-scheme AgBr/Ag/m-Bi5O7I (denoted as AAmB) was constructed via a photodeposition method. AAmB exhibited excellent photocatalytic degradation performance towards methylene blue (MB) under visible light illumination with apparent rate constants (0.01047 min−1), and it is approximately 4 times higher than that of AgBr/Ag/orthorhombic-Bi5O7I (plate-shaped) (called as AAoB) (0.00267 min−1) prepared at pH 12.5. Besides, the specific surface area of as-constructed AAmB heterojunction (18.5 m2·g−1) was also higher than that of AAoB (1.0 m2·g−1). These results indicate that the phase structure of Bi5O7I influences the morphology and specific surface area of the heterojunction. Furthermore, AAmB showed superior photodegradation activity for other pollutants, such as tetracycline (TC), bisphenol A (BPA), rhodamine B (RhB), etc. When bismuth nitrate was used as a raw material, only o-Bi5O7I was obtained at a wide pH range from 12 to 13, and the photocatalytic performance of the as-constructed AgBr/Ag/o-Bi5O7I heterojunction based on this o-Bi5O7I was notably lower than that of AAmB.