Defect (vacancy) engineering can modulate the catalyst surface atoms and electrons, which is a low-cost and effective modification strategy for Z-scheme heterojunction . In this paper, metal and non-metal double vacancies (V Zn+O ) Z-scheme heterojunction photocatalysts (BiOCl/ZnS−V Zn+O ) were synthesized for the degradation of norfloxacin (NOR) for the first time. The results show that the built-in electric field of BiOCl/ZnS−V Zn+O catalyst induces the directional migration of photogenerated carriers, which greatly improves the carrier migration and separation efficiency. The introduced nonmetallic (O) vacancies can lower the conduction band of BiOCl, while the metallic (Zn) vacancies can enhance the valence band of ZnS. Due to the synergistic efficiency formed by the double vacancies and Z-scheme heterojunction, BiOCl/ZnS−V Zn+O showed excellent performance in photodegradation of NOR (97.9% degradation rate of 20 mg/L NOR in 50 min photodegradation). In addition, the mechanism of action, intermediates and degradation pathways of photodegradation were discussed in detail.
In this study, a novel ternary photocatalyst, composed of BiOCl, ZnS, and ZnO, was successfully prepared for the first time via a mixed method followed by thermal treatment, which possessed a dual Type-II heterojunction structure. This composite exhibited substantially boosted photocatalytic degradation efficiency toward tetracycline (TC) under simulated sunlight. The microstructure, crystal morphology, charge transfer properties, and optical absorption behavior of the composite were systematically characterized and analyzed. The results demonstrated that the dual type-II heterojunction formed among ZnS, ZnO, and BiOCl effectively broadened the light absorption range and promoted the separation of photogenerated carriers, thereby significantly enhancing the photocatalytic activity. Active species trapping experiments and ESR tests confirmed that ·OH and ·O 2 - were the main active species in this photocatalytic system. The degradation efficiency of TC by this ternary catalyst under visible light reached as high as 95.8%, and it still maintained excellent stability after five consecutive cycles. Band structure analysis further revealed the charge separation mechanism in the dual type-II heterojunction. This novel dual type-II heterojunction is expected to provide new insights into the efficient degradation of pharmaceutical pollutants.
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