Enhanced photocatalytic degradation of methyl orange and metoprolol using a novel ternary TiO ₂ -ZnO/g-C ₃ N ₄ composite: performance under UV and visible light irradiation

Abstract Novel ternary photocatalyst TiO 2 -ZnO/g-C 3 N 4 was synthesized via a ball milling-assisted sol-gel method and its photocatalytic performance was tested in the photocatalytic degradation of methyl orange (MO) and metoprolol (MTP) under UV-LED and visible light. The samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen physisorption (BET), UV-visible diffuse reflectance spectroscopy (UV–Vis DRS), X-ray photoelectron spectroscopy (XPS) and positive hole production. Optical measurements confirmed that the combination of TiO 2 , ZnO, and g-C 3 N 4 extended the visible light absorption to 2.63 eV. SEM, TEM, FTIR and XPS revelated correct coupling between the three semiconductors, and hole density analysis suggested a synergistic effect, reducing the charge recombination. Additionally, reusability tests demonstrated the chemical stability of the material. In terms of pollutant degradation, the TiO 2 -ZnO/g-C 3 N 4 composite efficiently removed 97.75 % of MO under UV-LED light and 98.57 % under visible light in 180 min. Similarly, MTP degradation test reached 86.42 % and 86.08 % under UV-LED and visible light, respectively, after 180 min. These results highlight the mate-rial’s potential for environmental applications, particularly in contaminant removal through photocatalysis.