Photocatalytic Activity and Mechanism of Cu2+ Doped ZnO Nanomaterials

The photocatalytic activity and mechanism of photocatalysts made of ZnO nanoparticles before and after doping with different Cu 2+ 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 Cu 2+ doping. With the increase in doping concentration, the CuO and Cu 2 O 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 Cu 2+ , V + O , and Zn–H complexes. Photocatalytic degradation results of methyl orange showed that proper doping ( c (Cu 2+ ) = 2%) could improve the photocatalytic activity of ZnO. The main reason for the increase was that the substitution of Cu 2+ for Zn 2+ in the crystal lattice produced Zn i , 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.