Photocatalytic degradation properties of Ni(OH)_2 nanosheets/ZnO nanorods composites for azo dyes under visible-light irradiation

摘要

A new visible-light sensitive photocatalyst, Ni(OH)_2 nanosheets/ZnO nanorods composites with different Ni(OH)_2 contents, was synthesized via a facile water bath route. X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis spectroscopy were used to examine the morphology and microstructure of the composites. XRD analysis revealed that the two phases were composed of well crystallized ZnO and poorly crystallized Ni(OH)_2 - 0.75H_2O. Ni(OH)_2/ZnO composites showed a red shift in band edge absorption peak in the UV-vis absorbance spectrum, which enhanced their photocatalytic activity. The composites were used for the photodecolourization of water solution of representative organic azo dyes (rhodamine B (RB), Congo red (CR), methylene blue (MB) and methyl orange (MO)) under visible light. All synthesized composites showed better photodegradation performance compared to either pure ZnO or Ni(OH)_2. It was noted that composites removal rate strongly depended on the Ni(OH)_2 content. When Ni(OH)_2 fraction was 10 wt% composites exhibited maximum photodegradation performance for all organic azo dyes. Finally, the possible formation mechanism of the Ni(OH)_2/ZnO composites and their photocatalytic decomposition mechanism were also proposed and discussed.