Surface defects engineered Bi4Ti3O12 nanosheets for photocatalytic degradation of antibiotic levofloxacin

Surface defects have a significant effect on the photocatalytic reaction of Bi4Ti3O12, but the mechanism is unclear. In addition, when surface defects and highly exposed facets exist at the same time, which factor plays the main role in photocatalytic activity is also controversial. Herein, it is found that Bi4Ti3O12 with adjustable concentrations of surface defects and percentage of exposed {001} facets can be prepared by using titania of different crystal types and sizes as raw materials, which is extremely beneficial for exploring the above problems. The photocatalytic activity of Bi4Ti3O12 nanosheets with surface defects and exposed {001} facets was the same as that of Bi4Ti3O12 nanosheets with surface defects alone (about 72.5% of photodegradation levofloxacin under 10 min of simulated sunlight irradiation). Based on the experimental results and density functional theory calculations, the influence mechanism of surface defects was deeply studied. The surface defects resulting from partial exfoliation of the external (Bi2O2)2+ layers changed band structure of Bi4Ti3O12. More importantly, surface defects with high concentration became hole trapping sites, which was conducive to the faster participation of holes in the photocatalytic oxidation process.