Zn(II)-Doping Enhanced Photocatalytic Activity of Cu2O Nanocrystals

Zn(II)-doped octahedral and hexahedral Cu2O nanocrystals were synthesized with a green and gentle process. It was found that Zn-doping both tuned the Cu2O polyhedrons into quasi-spheres and decreased their sizes. The reduced lattice parameter as demonstrated in X-ray diffraction patterns (XRD), the increased binding energy of Cu(I) in X-ray photoelectron spectrum (XPS) and the uniform elemental distribution as exhibited in energy dispersive spectroscopy (EDS) mapping image provided solid evidence for the successful doping of Zn(II) in Cu2O nanocrystals. Zn(II) was verified to be surface enrichment, which might protect Cu2O from oxidation. Enhanced photocatalytic activity was observed with the degradation of methyl orange (MO) and methylene blue (MB) as the model reactions when the Zn-doping concentration was lower than 1%. UV-visible absorption spectra of the Zn-doped products showed red-shift in comparison with the pure Cu2O counterparts. The decreased band gap and the retarded oxidation were believed to be responsible for the improved catalytic activity. This method provides a new idea for the controlled synthesis of other doping materials and the study of the related photocatalytic activity.