Plasmonic resonance and type-I heterojunction interface in SrTiO₃/CZTS/Ag nanocomposite for enhanced photocatalytic degradation of organic pollutants

As a novel plasmonic-heterostructure photocatalyst, the Silver (Ag)-modified SrTiO₃/Cu₂ZnSnS₄ ternary nanocomposite was prepared through a co-precipitation method. The incorporation of Cu₂ZnSnS₄ (CZTS) and Ag into the SrTiO₃ host phase reduced the mean particle size from 65 to 38 nm, doubled the surface area, and decreased the bandgap energy from 3.20 to 2.86 eV. A study of UV–visible diffuse reflectance spectroscopy (DRS) and valence band X-ray photoelectron spectroscopy (VB-XPS) confirmed the formation of type-I heterostructure charge transfer mechanisms between SrTiO₃ and CZTS phases. Results from photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and transient photocurrent experiments indicated that the ternary nanocomposite exhibits less internal resistance and a higher capacity for charge carrier separation. The effect of different photocatalytic experiment parameters on the photodegradation performance has been studied. In this regard, 90 min visible light irradiation time, 5 mg/L initial dye concentration, and 1 g/L powder dosage were found to be the best values. The designed system exhibited excellent photocatalytic performance, in which more than 99% of methylene blue (MB) dye degraded under optimum conditions. The reaction mechanism and kinetics were comparatively investigated in-depth. After a four-run cyclic experiment, the prepared photocatalyst exhibited high stability and reusability. The prepared sample demonstrated photocatalytic efficiencies of 87%, 66%, and 71% for the degradation of methyl orange (MO), Rhodamine-B (RhB), and Ciprofloxacin (CIP) pollutants, respectively.