Bi2S3/Bi2O3 nanocomposites as effective photocatalysts for photocatalytic degradation of tetracycline under visible-light exposure

A modified simple sol-gel process based on the nonionic surfactant Pluronic F-127 has synthesized bismuth oxide (Bi2O3). A series of Bi2S3/Bi2O3 nanocomposites with varying Bi2S3 content (1.0–4.0 wt%) have been prepared and used as efficacious photocatalysts for tetracycline (TC) photodegradation via visible-light illumination. The physicochemical characterization of the Bi2S3/Bi2O3 samples revealed that mesoporous Bi2S3 nanoparticles (NPs) were successfully incorporated onto the surface of Bi2O3, forming heterojunctions that promote both charge transfer and harvesting of visible light with decreasing the charge carriers' recombination. The amount of Bi2S3 determines the effectiveness of the heterojunctions in the Bi2S3/Bi2O3 nanocomposites, with 3.0 wt% of Bi2S3 achieving the best development by decreasing the bandgap to 1.9 eV while enhancing the absorption of visible light. After 90 min of light illumination, the 3 wt% Bi2S3/Bi2O3 nanocomposite demonstrated the highest photocatalytic activity towards TC degradation, with a 2-fold greater than bare Bi2O3 NPs. By optimizing the dose to 2.0 g/L, the 3 wt% Bi2S3/Bi2O3 accomplished a quick photocatalytic degradation of TC solution at a rate constant of 0.0466 min−1. Furthermore, it maintained notable reusability after five runs after 60 min of exposure. The boosted photocatalytic efficiency of the Bi2S3/Bi2O3 photocatalyst is suggested by a Z-scheme mechanism in which the photogenerated electrons in Bi2O3 prefer to associate with the photogenerated holes in Bi2S3 due to their matched band locations. This study reinforces the application of nanoheterojunction oxides in quickly eliminating antibiotic contamination under visible light.