Enhanced photocatalytic degradation performance of BiVO4/BiOBr through combining Fermi level alteration and oxygen defect engineering

Constructing oxygen vacancies (Ov) has been widely used to enhance photocatalytic activity as a conventional and efficient approach, but its influence on the interfacial charge transfer pathway remains ambiguous. Herein, we synthesized BiVO4/BiOBr-Ov (BVB-Ov) photocatalysts through a facile method. Subsequently, various characterization results verified the successful preparation of BVB-Ov composites via combining BiVO4 with BiOBr containing oxygen vacancies (BiOBr-Ov). The results of photocatalytic degradation experiments illustrated that 20% BVB-Ov exhibited the highest degradation rate (91%) for Oxytetracycline (OTC), which was much higher than that of 20% BiVO4/BiOBr (71%). In addition, three possible degradation pathways were deduced from liquid chromatography-mass spectrometry (LC-MS) analysis. Photoelectrochemical, photoluminescence (PL) and time-resolved PL (TRPL) investigation revealed that 20% BVB-Ov possessed the fastest photogenerated carrier separation and transportation rate. Kelvin probe force microscopy (KPFM) technology and Density functional theory (DFT) calculations have shown that the introduction of oxygen vacancies modulated the relative positions of the Fermi levels between BiVO4 and BiOBr. We have finally combined DFT calculations, energy band analysis, trapping experiments and electron paramagnetic resonance (EPR) results, confirming that the existence of oxygen vacancies led to altering the photogenerated carrier transfer path from type-II to Z-scheme. This work provided insights and guidelines for oxygen vacancies to coordinate interfacial charge transfer pathways.