Hydrothermal Synthesis and Photocatalytic Activity of Zinc Oxide Hollow Spheres

TLDR

ZnO hollow spheres are of interest for solar cells, catalysis, separation, biomedical engineering, and nanotechnology. ZnO hollow spheres were synthesized by one‑pot hydrothermal treatment of glucose/ZnCl₂ at 180 °C for 24 h followed by calcination, and their photocatalytic activity was assessed by Rhodamine B decolorization at ambient temperature. Varying the glucose‑to‑zinc molar ratio controls crystallite size, shell thickness, surface area, and pore structure, with the highest photocatalytic activity at R = 15, and the spheres can be easily separated and reused without significant loss of activity.

Abstract

ZnO hollow spheres with porous crystalline shells were one-pot fabricated by hydrothermal treatment of glucose/ZnCl2 mixtures at 180 °C for 24 h, and then calcined at different temperatures for 4 h. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption−desorption isotherms. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic decolorization of Rhodamine B aqueous solution at ambient temperature. The results indicated that the average crystallite size, shell thickness, specific surface areas, pore structures, and photocatalytic activity of ZnO hollow spheres could be controlled by varying the molar ratio of glucose to zinc ions (R). With increasing R, the photocatalytic activity increases and reaches a maximum value at R = 15, which can be attributed to the combined effects of several factors such as specific surface area, the porous structure and the crystallite size. Further results show that hollow spheres can be more readily separated from the slurry system by filtration or sedimentation after photocatalytic reaction and reused than conventional powder photocatalyst. After many recycles for the photodegradation of RhB, the catalyst does not exhibit any great loss in activity, confirming ZnO hollow spheres is stability and not photocorroded. The prepared ZnO hollow spheres are also of great interest in solar cell, catalysis, separation technology, biomedical engineering, and nanotechnology.