Photocatalytic Activity and Mechanism of Cu2+ Doped ZnO Nanomaterials

Abstract

The photocatalytic activity and mechanism of photocatalysts made of ZnO nanoparticles before and after doping with different Cu2+ concentrations were studied by electron paramagnetic resonance and X-ray diffraction. The nanoparticles were prepared using sol–gel method. UV-vis spectrometers characterized the photocatalytic degradation effect of the composite samples on methyl orange solution. The results of X-ray diffraction showed that the hexagonal wurtzite structure of ZnO changed little by Cu2+ doping. With the increase in doping concentration, the CuO and Cu2O diffraction peaks were detected successively in the crystal. The results of the electron paramagnetic resonance test for all samples indicated three kinds of unpaired electrons with g factors of 2.07, 1.997, and 1.954. Further analysis confirmed them to be Cu2+, V+O, and Zn–H complexes. Photocatalytic degradation results of methyl orange showed that proper doping (c(Cu2+) = 2%) could improve the photocatalytic activity of ZnO. The main reason for the increase was that the substitution of Cu2+ for Zn2+ in the crystal lattice produced Zni, and the Zn atom could act as the donor to release electrons, so that the number of electrons in the material increased, which indirectly increased the superoxide radical content in the solution and improves the photocatalytic activity of ZnO.