A facile approach to fabrication of well-dispersed NiO–ZnO composite hollow microspheres†
A novel, facile and template-free approach was developed for the fabrication of amorphous zinc-nickel citrate hollow microspheres and crystalline well-dispersed NiO–ZnO composite hollow microspheres. In this approach, amorphous zinc-nickel citrate hollow microspheres were prepared through a simple chemical reaction and with room temperature ageing at nickel nitrate solution. The zinc-nickel citrate hollow microspheres have an average size of about 1.4 μm. The average thickness of the shell is about 300 nm. The content of Ni in the zinc-nickel citrate can be simply adjusted by changing the ageing time. The well-dispersed NiO–ZnO composite hollow microspheres can be prepared via the perfect morphology inheritance of the zinc-nickel citrate hollow microspheres, by calcination at 500 °C for 2 h. The optical absorption of the samples can extend into the visible region after the loading of NiO. The NiO–ZnO composite hollow microspheres with the high content of NiO exhibit the highest photocatalytic activity for the degradation of different organic dyes including Rhodamine-B, methylene blue and methyl orange under UV irradiation, which might be ascribed to their highest separation efficiency of photogenerated electron–hole pairs. In addition, these NiO–ZnO composite photocatalysts can be used repeatedly without a significant decrease of the photocatalytic activity under UV irradiation.