Dual-wavelength laser-driven TCH degradation over ZnO/cu₁.₃₅O/g-C₃N₄ S-scheme heterojunctions: Charge-transfer...

A ZnO/Cu₁.₃₅O/g-C₃N₄ ternary heterojunction was constructed via a sequential calcination-hydrothermal route for mixed-laser-driven photocatalytic degradation of tetracycline hydrochloride (TCH). Owing to rational band alignment and strong interfacial coupling, the optimized ZCG-2 catalyst achieved efficient TCH removal at an initial concentration of 30 ppm, with degradation efficiencies of 98.99%, 96.63%, and 99.02% under 450 nm, 660 nm, and mixed-laser irradiation, respectively, under the present experimental conditions. Spectroscopic and electrochemical analyses revealed enhanced charge separation and interfacial transfer in ZCG-2, while VB-XPS, trapping experiments, EPR, and femtosecond transient absorption spectroscopy collectively supported an S-scheme charge-transfer pathway involving h⁺, ·O₂^-, and ¹O₂ as the major reactive species. In addition to rapid pollutant removal, the optimized system exhibited substantial mineralization, with a TOC removal efficiency of about 84% after 90 min. Soybean germination assays further indicated improved biological safety after photocatalytic treatment. These results demonstrate that mixed-laser excitation combined with ternary S-scheme heterojunction engineering provides an effective strategy for efficient TCH degradation and mineralization.