One-pot synthesis of the visible light sensitive C-doped ZnO@g-C3N4 for high photocatalytic activity through Z-scheme mechanism

Abstract

ZnO/g-C3N4 composite was prepared through thermal treatment of commercially available ZnO nanoparticles and melamine. The prepared samples with different ZnO loading were characterized by several techniques such as X-ray diffraction (XRD), ultraviolet visible diffuse reflectance spectroscopy (UV–vis), infrared spectroscopy (IR), Raman spectroscopy, scanning electron microscopy (SEM), and finally, transmission electron microscopy (TEM). Characterization data confirmed the uniform combination of ZnO and g-C3N4 phases, moreover, it was observed that ZnO nanoparticles were doped with carbon during the synthesis, i.e. two different functionalization in one synthesis step. Moreover, the prepared composite C-doped ZnO@g-C3N4 showed a clear red shift adsorption as a function of ZnO concentration. The photocatalytic performance of the prepared samples was investigated in the decolourization of methyl green dye, as a model reaction, under visible light with a wavelength greater than 425 nm. The photocatalytic activity of the composite was superior to other tested photocatalysts, the decolourization rate constant was almost 4 times higher than neat ZnO, neat g-C3N4 or even C-doped ZnO. The stability of the composite was evaluated through performing four consecutive reactions without any kind of treatment to the composite. The obtained results indicate the high stability of the composite.