Enhanced activity of ZnO with addition of C3N4 for photocatalytic removal of phenol under visible light

Abstract

Phenol is a stable and hazardous compoundthat is commonly found as an industrial effluent 1. Phenol can be treated by photocatalysis using ZnO as a photocatalyst'' 3. Unfortunately, the use of zinc oxide (ZnO) in photocatalysis is limited due to the photocorrosion effect and poor response to the visible light", Various methods have been reported to improve the performance of ZnO,such as the use of carbon nitride (C3N4) to suppress the photocorrosion and improve the absorption in the visible light regions. It was reported that the ZnO-C3N4could be prepared by mixing the powder ZnO with C3N4that was dispersed in methanol, followed by drying process under nitrogen atmospheres. In the present study, a series of ZnO-C3N4was prepared bya simplermethod, which was impregnationof zinc oxide precursor on the C3N4, followed by calcination process. The effect of zinc to carbon ratio (Zn/C) on the properties and photocatalytic activity was examined.XRD patterns of the samples revealed that as the Zn/C ratio increased, the intensity of diffraction peaks for ZnO also increased but the intensity for C3N4 decreased. All the prepared composite materials have an extended absorption band in the visible light region due to the presence of C3N4, as supported by DR-UV Vis spectra. The prepared ZnO-C3N4 composites were further investigated in the photocatalytic removal of phenol under visible light irradiation for 5 hours. All ZnO-C3N4 samples showed higher activity than the bare ZnO (Figure 1). The ZnO-C3N4 with Zn/C ratio of 1 mol% showed the highest photocatalytic activity for removal of phenol among all the samples. The high activity observed on the ZnO-C3N4 would be due to the role of C3N4 to suppress electron-hole recombination and extend the absorption ofZnO in the visible light region.