Band-gap engineering of Bi4O5I2 via Sn4 + doping for highly efficient solar-light-responsive photocatalysis

Ion doping represents a viable strategy for improving the photocatalytic performance of semiconductor materials. This study successfully synthesized Sn 4+ -doped Bi 4 O 5 I 2 photocatalysts through an in-situ calcination approach. Structural characterization confirmed that Sn 4+ incorporation induced lattice contraction while increasing the density of active surface sites. Photocatalytic evaluation revealed that the 10 % Sn-BOI catalyst achieved 95.4 % levofloxacin (LOFX) degradation within 40 min under visible light irradiation, exhibiting a reaction rate constant (k) 5.2-fold greater than undoped Bi 4 O 5 I 2 . The catalyst demonstrated excellent stability, retaining high activity through four consecutive recycling tests. Mechanistic studies showed that oxygen vacancies (OVs) generated during doping modified the electronic structure by elevating the valence band maximum and narrowing the bandgap, while simultaneously promoting charge separation through electron trapping. These findings establish an effective methodology for developing photocatalysts to address antibiotic pollution in wastewater.