Synthesis and characterization of successive Z-scheme CdS/Bi2MoO6/BiOBr heterojunction photocatalyst with efficient performance for antibiotic degradation

Highlights: • A novel CdS/Bi₂MoO₆/BiOBr photocatalyst was synthesized with successive heterojunction. • CdS/Bi₂MoO₆/BiOBr has good catalytic activity for tetracycline hydrochloride. • The catalyst has a good separation efficiency of photogenerated electron-hole pairs. • The catalyst shows excellent cycle stability. -- Abstract: A novel CdS/Bi₂MoO₆/BiOBr successive Z-scheme photocatalyst has been synthesized by a solvothermal-precipitation method. The structure, composition, morphology and optical property of the ternary composite were investigated. The maximum degradation rate of CdS/Bi₂MoO₆/BiOBr for tetracycline hydrochloride (TC) can reach 94.41% under visible light, while its degradation rate was 10.43, 2.89, and 2.43 times higher than that of pure Bi₂MoO₆, BiOBr and Bi₂MoO₆/BiOBr, respectively. Besides, the CdS/Bi₂MoO₆/BiOBr composite showed stable catalytic performance after three successive reuses. The improved photocatalytic and stability could be ascribed to the extended visible-light absorption capability, effective separation of electron-hole pairs and layered stable structure. Photoluminescence spectroscopy and electrochemical impedance spectroscopy proved that the composite had more efficient charge separation efficiency. The energy band structure and free radical capturing experiments proved that the redox reaction mainly occurred in the conduction band of CdS and the valence band of BiOBr in this composite, so a possible successive Z-scheme heterojunction mechanism is proposed. This work also provides a feasible idea for the treatment of TC in wastewater.