Oxygen vacancy defect engineering in MoO2/Mo-doped BiOCl Ohmic junctions for enhanced photocatalytic antibiotic elimination

Vacancy defect engineering is an effective strategy for improving photocatalytic activity, but controlling surface vacancies precisely remains a challenge. In this study, MoO2/Mo doped BiOCl (Mo-BiOCl) composites enriched with oxygen vacancies (OVs) were prepared by a facile defect engineering strategy with MoO2 hollow spheres as a precursor and molybdenum sources, where the slowly released Mo4+ ions in the reaction system resulted in the tailored formation of Mo-BiOCl. The optimized MoO2/Mo-BiOCl composite (BOM-3) demonstrated significantly improved photocatalytic degradation efficiency for Tetracycline hydrochloride (TC) under visible light, with an apparent rate constant (k) 4.7 and 120 times higher than that of BiOCl and MoO2, respectively. The enhanced photocatalytic activity of BOM-3 can be attributed to the presence of abundant OVs, which extend the light response range by creating intermediate defect level from OVs. Additionally, the formation of ohmic heterojunction between Mo-BiOCl and MoO2 with close interface contacts facilitates rapid separation of interfacial charge carries and efficient migration of photogenerated electrons from Mo-BiOCl to MoO2. The possible degradation pathway of TC using BOM-3 is proposed, and toxicity evaluation indicates that most intermediates have lower toxicity than TC. This work presents a straightforward approach for improving photocatalytic antibiotic degradation through the construction of a novel Ohmic-junction with tuned surface OVs.