Microwave-assisted synthesis of a TiO2-CuO heterojunction with enhanced photocatalytic activity against tetracycline

A microwave method was used for the synthesis of TiO2-CuO oxide systems. A detailed investigation was made of the effect of the molar ratio of components (TiO2:CuO = 9:1, 7:3, 5:5, 3:7, 1:9) on the crystalline structure and morphology. Transmission electron microscopy (TEM) confirmed the presence of octahedral and rod-shaped titania particles and sheet copper(II) oxide particles; moreover, HRTEM analysis indicated the presence of a heterojunction between TiO2 and CuO. The synthesized materials were analyzed by X-ray diffraction (XRD) and Raman spectroscopy, and two crystalline forms (anatase and monoclinic CuO) were detected. The key element of the work was to determine the photocatalytic activity of the obtained binary oxide systems in the degradation of tetracycline. Photo-oxidation tests proved that the binary oxide materials (especially the (9)TiO2-(1)CuO and (7)TiO2-(3)CuO samples) demonstrate high photocatalytic activity in the decomposition of tetracycline (95% after 90 min irradiation) compared with the reference titania samples. Furthermore, a Z-scheme heterojunction photocatalytic process mechanism was proposed. Another important part of the work was the determination of tetracycline photodegradation products using the HPLC/MS technique.