Hierarchical 0D/3D Z-scheme heterojunction of ZnO quantum dots/flower-like Bi2MoO6 microspheres for efficient photocatalytic degradation of tetracycline†

The rapid development of modernization has accelerated environmental degradation, and antibiotic-induced water pollution has become one of the most concerning issues. In this study, a Z-scheme heterojunction catalyst of ZnO quantum dots (QDs)/Bi₂MoO₆ with a hierarchical 0D/3D structure was fabricated via a simple ultrasonic impregnation method for the photodegradation of the representative antibiotic tetracycline (TC). This hierarchical 0D/3D heterojunction consists of flower-like Bi₂MoO₆ microspheres assembled from nanosheets and ZnO QDs decorated on the nanosheets. The photocatalytic activity of the optimal heterojunction catalyst 8%ZnO QDs/Bi₂MoO₆ was 1.81 times that of pure Bi₂MoO₆. The enhanced photocatalytic activity of 8%ZnO QDs/Bi₂MoO₆ results from its broadened light absorption and efficient separation of photogenerated charge carriers, as evidenced by UV-vis DRS, photoluminescence spectroscopy, and transient photocurrent response. Under optimal degradation conditions, the photocatalytic degradation efficiency of TC by 8%ZnO QDs/Bi₂MoO₆ reached 94.20% within 120 min under simulated sunlight. Furthermore, 8%ZnO QDs/Bi₂MoO₆ exhibited robust performance in a complex environment. Additionally, combining the results of active species trapping experiments, the Mott–Schottky curve, and band structure analysis, a Z-scheme photocatalytic mechanism for the 8%ZnO QDs/Bi₂MoO₆ heterojunction was proposed. This work offers a sustainable solution for real aqueous environment remediation.