Design of CdS/BiOI/ZnO efficient double Z-type heterojunctions and their photocatalytic degradation of rhodamine B

In this paper, a novel ternary composite photocatalyst of CdS/BiOI/ZnO was synthesized by the solvothermal method for dual applications in the degradation of organic dyes and the reduction of hexavalent chromium (Cr(VI)). The composite was systematically characterized using XRD, SEM, TEM, BET, UV–Vis DRS, PL and EIS. Photocatalytic performance tests revealed that the ternary composite exhibited excellent activity toward both RhB and MB degradation. After 30 min of irradiation with a 70 W metal halide lamp, the degradation efficiency of 50 mg/L RhB was 98.31%, and that of 50 mg/L MB was 85.32%. In addition, in the heavy metal pollution simulation experiment, after being exposed to a 70 W for 30 min, the degradation efficiency of 50 mg/L Cr (VI) was 90.37%. Radical trapping experients indicated that h⁺ and O₂⁻ served as the primary active species, with ·OH playing a secondary role. A plausible double Z-scheme charge transfer mechanism was proposed.