Flower-like Bi ₂ SiO ₅ /Bi ₄ MoO ₉ heterostructures for enhanced photocatalytic degradation of ciprofloxacin

Abstract

Bi₂SiO₅/Bi₄MoO₉ photocatalysts with heterostructures were successfully prepared using a one-pot solvothermal route. The effect of the molybdenum source on composite formation is discussed. Under ultraviolet light irradiation, the Bi₂SiO₅/Bi₄MoO₉ heterojunction photocatalyst exhibited higher photocatalytic performance than Bi₂SiO₅ and Bi₄MoO₉ towards the degradation of ciprofloxacin (CIP). This dramatically enhanced photoactivity can be ascribed to the construction of a heterojunction interface between Bi₂SiO₅ and Bi₄MoO₉, which not only suppresses the recombination of photoexcited charge carriers but also enhances light absorption. In addition, from a practical point of view, the the effect of initial CIP concentration and coexisting ions on the photodegradation process using as-prepared Bi₂SiO₅/Bi₄MoO₉ heterojunction photocatalysts was explored. Trapping experiments demonstrate that photoexcited holes and superoxide radicals are the main active species in the photodegradation of CIP over Bi₂SiO₅/Bi₄MoO₉ heterojunctions. Meanwhile, the conduction band and valence band potentials of Bi₂SiO₅ and Bi₄MoO₉ were measured by density functional theory calculation, diffuse reflectance spectroscopy and Mott-Schottky curves. A possible photocatalytic mechanism for CIP degradation over the Bi₂SiO₅/Bi₄MoO₉ heterojunction is proposed.