Interfacial engineering of Cd0.5Zn0.5S/BiOBr S-scheme heterojunction with oxygen vacancies for effective photocatalytic antibiotic removal

The construction of S-scheme heterojunction photocatalysts has emerged as a promising strategy to address the urgent need for efficient antibiotic wastewater remediation. However, persistent challenges in achieving interfacial intimacy and precise charge transfer regulation between semiconductors have hindered their practical implementation. In this work, we engineered a hierarchical Cd_0.5Zn_0.5S/BiOBr S-scheme heterojunction via a controlled solvothermal synthesis, where BiOBr microspheres serve as the core, and Cd_0.5Zn_0.5S nanoparticles form a conformal shell. This architecture ensures maximal interfacial contact and directional charge dynamics, critical for optimizing photocatalytic efficiency. The optimized heterojunction exhibits superior catalytic performance, achieving tetracycline (TC) degradation rate constants 3.3- and 1.6-fold greater than pristine BiOBr and Cd_0.5Zn_0.5S, respectively. This enhancement stems from the synergistic interplay of efficient charge separation and preserved redox capacities inherent to the S-scheme mechanism. Furthermore, the TC degradation process and mechanism were elucidated. This study provides a new perspective on developing defective S-scheme heterojunctions for antibiotic wastewater purification with high performance.