Fabrication of TiO_2 hollow microspheres by ammonia-induced self-transformation

摘要

TiO_2 hollow microspheres (TiO_2-HMSs) have attracted great interest in recent years due to their unique physical and chemical properties such as low density, high surface area and effective light-harvesting property. In this paper, anatase TiO_2-HMSs were synthesized by hydrothermal treatment of amorphous TiO_2 microspheres precursor in the presence of ammonia solution at 180 °C. The prepared TiO_2-HMSs were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscopy (SEM). It was found that the presence of ammonia accelerates the hollowing process of TiO_2 microspheres, and the phase transformation from amorphous TiO_2 to metastable ammonium tita-nate occurs firstly and then to anatase TiO_2 phase, forming fluffy core/shell and yolk/shell structured microspheres. The photocatalytic activity of the photocatalyst was evaluated both by photocatalytic degradation of cationic dye (Rhodamine B) and anionic dye (Brilliant Red X-3B) under UV irradiation. The calcined fluffy core/shell structured TiO_2 microspheres with a hydrothermal reaction time of 18 h showed the highest photocatalytic activity. Ammonia-induced self-transformation mechanism was also proposed for the formation of TiO_2-HMSs.