Dual-Functional Plasmonic Z‑Scheme Bi2WO6/Ag/CuS Ternary Nanocomposite for Photocatalytic Oxidation of Tetracycline and Reduction of Cr (VI) under Visible Light.

The simultaneous removal of antibiotic pollutants and toxic heavy metals from wastewater remains challenging because of limited visible-light utilization and rapid recombination of photogenerated charge carriers in conventional photocatalysts. Integrating plasmonic nanostructures into semiconductor heterojunctions provides an attractive route to simultaneously enhance light harvesting and photocatalytic redox activity. In this work, a plasmonic Bi2WO6/Ag/CuS ternary nanohybrid was fabricated through sequential photodeposition of Ag nanoparticles onto hierarchical Bi2WO6 microspheres, followed by the in situ growth of CuS. The incorporation of Ag nanoparticles promotes interfacial charge transfer and enhances visible-light harvesting through the surface plasmon resonance effect. The photocatalytic activity of the ternary nanohybrid was assessed through tetracycline (TC) oxidation and Cr (VI) reduction under visible-light irradiation. The optimized ternary nanohybrid achieved 92% TC degradation and 90% Cr (VI) reduction within 60 min, corresponding to apparent rate constants of 0.0336 and 0.0322 min-1, respectively. Furthermore, enhanced removal efficiencies were observed in the coupled TC/Cr (VI) system, indicating a synergistic interaction between oxidation and reduction processes. Band-structure analysis and in situ EPR measurements verified the Ag-mediated all-solid-state Z-scheme charge-transfer pathway. LC-MS analysis and phytotoxicity assessment revealed the progressive degradation of TC into less toxic intermediates. The photocatalyst also exhibited good stability and considerable activity in real water matrices, highlighting its potential for practical solar-driven wastewater remediation.