Fabrication of Bi ₂ MoO ₆ /BiOBr S‑Scheme Heterojunctions with Enhanced Charge Separation for Efficient Visible Light Photocatalytic Degradation of Tetracycline

ABSTRACT Antibiotic residues in aquatic systems have become a severe environmental issue. Herein, a novel visible‑light‑driven Bi ₂ MoO ₆ /BiOBr (BMO/BOB) S‑scheme heterojunction was successfully synthesized by hydrothermal in situ precipitation methods. The phase structure, morphology, surface chemistry, optical, and photoelectrochemical properties were systematically characterized. The optimized 7‑BMO/BOB composite exhibits excellent photocatalytic activity toward tetracycline (TC) degradation, with a removal efficiency of 92.8% within 50 min, which is much higher than those of pure Bi ₂ MoO ₆ (74.0%) and BiOBr (87.9%). The kinetic rate constant reaches 0.048 min ^{− 1} , approximately 2.18 and 1.17 times that of Bi ₂ MoO ₆ and BiOBr, respectively. The improved photocatalytic activity of BMO/BOB S‑scheme heterojunction originates from the synergistic function of broadened visible light absorption range and accelerated charge separation efficiency. The S‐scheme charge transfer mechanism maintains the powerful reducing capacity of photogenerated electrons from BiOBr, as well as the strong oxidation property of holes derived from Bi ₂ MoO ₆ , thus generating abundant ·O ₂ ⁻ , h ⁺ , e ⁻ and ·OH active species for TC degradation. This study provides a feasible strategy for designing efficient bismuth‑based S‑scheme photocatalysts for antibiotic wastewater treatment.