Abstract: In this study, S-scheme-based hydrothermal synthesis of Ag-CuBi₂O₄/CNTs/Bi₂S₃ layered composites has been successfully reported. The photo-degradation of toxic dyes, viz. methyl orange (MO), and methylene blue (MB), has been used to examine nanocomposites with varying weight percent of Bi₂S₃ for photocatalytic activity in the visible range. Among candidates, Ag-CuBi₂O₄/CNTs/Bi₂S₃ with a 10% loading of Bi₂S₃ outperformed both pure and hybrid composites in photocatalytic activity. For MO degradation, the hybrid composite with 10% Bi₂S₃ loading degrades 7.04 times higher than pristine CuBi₂O₄ and Bi₂S₃ samples, and for MB degradation, it degrades 4.96 times higher than pristine samples. High surface area, less recombination rate of photogenerated charge carriers, photogenerated carriers faster separation, and high redox ability of Ag-CuBi₂O₄/CNTs/Bi₂S₃ (10%) are all attributed to the improving photocatalytic performance. Even after ten cycles, the hybrid composite is chemically stable and reusable. Carbon nanotubes (CNTs) are a transfer bridge in layered structure for electrons because of their coordinated Fermi level between Ag-CuBi₂O₄ and Bi₂S₃. In addition, the scavenger and electron spin resonance (ESR) experiments verified that ∙O₂^-, ∙OH, and h⁺ were the important reactive species that successfully facilitated the photocatalytic degradation process to degrade dyes. This study presents a straightforward and economical approach for obtaining a stable semiconductor-based photocatalytic system and a potential technique for future applications.

Key words: Ag-CuBi₂O₄, Bi₂S₃, Carbon nanotubes (CNTs), S-scheme charge transfer, Dye degradation