Facile construction of Zn0.6Cd0.4S/Bi3O4Br S-scheme heterojunction with enhanced performance under visible light: An experimental and theoretical study

With the advancement of economy, the polluted water from industry is increasing day by day, which inevitably causes great harm to the environment. Photocatalytic technology based on solar energy is considered as one of the effective ways to treat organic pollutants in water because of its advantages of green, high efficiency and environment-friendly. A range of Zn 0.6 Cd 0.4 S/Bi 3 O 4 Br composites were synthesized via in-situ growth method. A comprehensive characterization of the morphology, crystal structure and photoelectronic properties was carried out using multiple techniques, including X-ray diffraction (XRD), Scanning Electron Microscope (SEM), X-ray Photoelectron Spectroscopy (XPS), photoluminescence (PL), Ultraviolet-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS) and Brunauer-Emmett-Teller (BET). The data from photocatalytic experiments showed that the composite had superior performance than the monomers, the degradation efficiency of methylene blue (MB), rhodamine B (RhB) and tetracycline (TC) reached 97.92 % (80 min), 98.55 % (70 min) and 97.61 % (40 min) respectively. Various water sources (pure water, tap water, lake water and seawater) and different pH conditions were taken into account during the experiments. The results showed that Zn 0.6 Cd 0.4 S/Bi 3 O 4 Br-35 % maintained comparable photocatalytic performance for both dyes and antibiotic in all solutions with different resources of water, indicating its remarkable adaptability across diverse water matrices. The most favored pH condition was neutral (pH = 7). It was confirmed by the radical trapping experiment that holes (h + ) and superoxide radicals (•O 2 - ) were vital to the photocatalytic process. The data from density functional theory (DFT) calculation confirmed that the electron transfer followed an S-scheme mechanism. The formation of S-type heterojunction separated the photogenerated electron-hole pairs effectively, and the Zn 0.6 Cd 0.4 S/Bi 3 O 4 Br-35 % exhibited tremendous potential for future implementations in photocatalytic degradation for organic pollutants.