One-Step Fabrication of the ZnO/g-C3N4 Composite for Visible Light-Responsive Photocatalytic Degradation of Bisphenol E in Aqueous Solution

The ZnO/g-C3N4 composite was successfully synthesized by a simple one-step calcination of a urea and zinc acetate mixture. The photocatalytic activity of the synthesized composite was evaluated in the degradation of bisphenol E (BPE). The morphology, crystallinity, optical properties, and composition of the synthesized composite were characterized by using various analytical techniques such as scanning electron microscopy (SEM), transmitted electron microscopy (TEM), field emission-electron probe microanalysis (FE-EPMA), nitrogen adsorption and desorption isotherm measurement, Fourier-transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The degradation rate of BPE with the ZnO/g-C3N4 composite was 8 times larger than that obtained with pure g-C3N4 at the optimal conditions. The excellent photocatalytic activity was attributed to the synergistic effect between the g-C3N4 and ZnO, which enhanced the efficiency of charge separations, reduced the e-/h+ pairs recombination, and increased the visible light absorption ability. The radical scavenger studies indicated that the •O2- and h+ species were mainly responsible for the degradation of BPE. The stability test suggested the chemical and photostability of the synthesized composite. Two possible photocatalytical mechanisms have been suggested.