Construction of S-scheme Ag/CdS/Fe₂O₃ heterojunction for photocatalytic degradation of amoxicillin under visible light

An S-scheme Ag/CdS/Fe₂O₃ (Ag/CS/FO) heterojunction was fabricated via a sequential solvothermal and photodeposition method. The microstructure and optoelectronic properties of the synthesized ternary composite were verified by a series of characterization methods. The transfer of photogenerated electron–hole pairs (e⁻/h⁺ pairs) follows an S-scheme pathway, driven synergistically by the interfacial electric field (IEF) and band bending. That directs electrons (e⁻) to the conduction band (CB) of CdS (CS) and holes (h⁺) to the valence band (VB) of Fe₂O₃ (FO), achieving efficient e⁻/h⁺ pairs separation while maintaining high redox capabilities. Additionally, the incorporated Ag nanoparticles enhance visible-light harvesting via the surface plasmon resonance (SPR) effect and function as electron-transfer bridges, collectively promoting charge migration. Consequently, the composite exhibits high photocatalytic activity, degrading 98.68% of amoxicillin (AMX) under visible light. It also maintains 91.6% efficiency after four cycles, confirming sound stability. Notably, the material demonstrates superior performance in real-life water matrices (tap and river water), highlighting its strong application potential.