High‐Efficiency S‐Scheme Bi 4 O 5 IBr / Bi 5 O 7 I 0 . 7 Br 0 .3 Double Solid Solution Heterojunction Photocatalyst for Levofloxacin Degradation via Optimized Carrier Dynamics

The remediation of antibiotic‐polluted water demands advanced photocatalytic systems with high efficiency and stability. This study constructs a novel double solid solution S‐scheme heterojunction by coupling Bi 4 O 5 IBr with Bi 5 O 7 I 0.7 Br 0.3 (BOIB) for the degradation of levofloxacin (LEV). The pivotal element of this design is the internal electric field (IEF) induced by the significant work function difference between the two solid solution components, as unequivocally confirmed by density functional theory (DFT) calculations. This IEF actively orchestrates the S‐scheme charge transfer pathway, which was directly verified by a suite of photoelectrochemical analyses: significantly quenched photoluminescence and shortened carrier lifetime attest to the efficient interface recombination of useless charges, while concurrently, a dramatically enhanced photocurrent response and decreased electrochemical impedance signal the successful spatial separation of powerful electrons and holes. This optimized carrier dynamics culminates in exceptional photocatalytic performance, achieving 88.4% degradation of levofloxacin under visible light. Furthermore, the degradation mechanism was deciphered to involve a synergistic action of multiple reactive species, where S‐scheme derived charges generate ·O 2 − /·OH while an energy transfer pathway yields singlet oxygen ( 1 O 2 ), as definitively identified by EPR spectroscopy. Coupled with outstanding stability (82.0% activity retention after 5 cycles), this work provides a mechanistic blueprint and a highly promising candidate for designing advanced photocatalytic systems for practical water purification.