Constructing Z-scheme AuAg@δ-Bi2O3/BiOBr multi-heterojunction for efficient photocatalytic removal of dye, antibiotic and heavy metal ions: Performance and mechanism investigation

The AuAg alloy nanoparticles were decorated on the δ-Bi2O3 surface to obtain AuAg@δ-Bi2O3, then AuAg@δ-Bi2O3 were hydrothermally combined with BiOBr plate to form Z-scheme AuAg@δ-Bi2O3/BiOBr. The photocatalytic activity of samples were evaluated by the removal of dyes (rhodamine B (RhB) and acid orange 7 (AO7)), tetracycline (TC) and reduction of Cr(VI) under simulated sunlight irradiation. With the decoration of δ-Bi2O3, the δ-Bi2O3/BiOBr composites exhibit higher photocatalytic activity than bare BiOBr. The optimal catalytic efficiency is achieved by 10%δ-Bi2O3/BiOBr sample, which leads to ∼75.7% of AO7, 84.9% of RhB and 67.5% of Cr(VI) removed after 25 min irradiation. After the introduction of AuAg nanoparticles, the photocataltyic activity of 10%δ-Bi2O3/BiOBr can be further enhanced. The removal efficiency of AO7, RhB and Cr(VI) can reach ∼97.9%, ∼97.3% and ∼84.5% after 25 min irradiation, respectively. The AuAg alloy nanoparticles located at the interface of Z-scheme δ-Bi2O3/BiOBr can accelerate the photogenerated charges separation over the way of a Z-scheme charge migration mechanism. In addition, AuAg alloy nanoparticles located at δ-Bi2O3 surface compensates the consumption of photogenerated charges in the direct Z-scheme δ-Bi2O3/BiOBr heterojunction due to their SPR effect, and even further promotes the separation of photogenerated charges in the composite.