Study On One-Step Approach To Synthesize Metal Doped Hollow Titania Microspheres And Its Photocatalytic Activity

Titanium dioxide has a good photoelectricity property and photochemistry stability, which makes it apply to many areas including photoelectricity conversion, solar engergy using and photocatalytic decompositon of pollutants. However, the wide band gap of titania can only be excitateded by the high energy ultraviolet. In order to expand the absorbance of titania to the visible light region to improve the photocatalytic efficiency, many improving ways have been studied and it is found that doping the transition metal ion is a very effective measure. Titania hollow microspheres with its interesting properties such as low density and high surface area can exhibit some unique capacity when it is doped. Therefore, the study of preparation and photocatalytic activity of metal ion-doped titania hollow microspheres has attracted wide atterntion of researchers.In this study, we propose a one-step approach to prepare metal ion-doped titania hollow microspheres which is different from the traditional template method. Positively charged polystyrene (PS) spheres are used as the templates and peroxo-titanium complex (PTC) act as the precursor. Without any surfactant they react and change into titania hollow microspheres just due to the strong electrostatic force. Also, it is doped with Fe3+ and V5+ and its photocatalytic activity is studied under visible light.The preparation method of titania hollow microsphere is firstly studied. After the as-samples are characterized by XRD, the content of PTC and the best reaction time are confirmed. It is obvious that the catalysts show pure anatase phase in such conditon. Through the characterization of SEM,TEM,FT-IR, it is certain that the antase titania microspheres have a hollow structure.Different concentration of iron and vanadium doped titania hollow microspheres are prepared by the one-step method respectively. It is characterized by XRD,SEM,TEM. The doped samples show pure anatase phase and better spherical morphology. The results of UV indicate that the doped samples can obviously enhance the absorption in the visible light region. Through the photocatalytic decompositon of methylene blue, both of the best doping concentration are confirmed which are 0.75% for iron and 1% for vanadium. When they are doped with the best concentration, the samples exhibit the best photocatalytic activity under visible light. The possible photocatalytic mechanism of doped TiO₂ hollow microspheres has been proposed.Doped 1% vanadium TiO₂ hollow microspheres are prepared by one-step method and traditional template method. Compared with the samples fabricated by traditional method, the samples synthesized by one-step method can avoid the the risk of the agglomeration and the collapse of the hollow structure which is brought by the process of calcination. The surface coating, removal of the core-material and the crystallization of the titania shell are finished simultaneously instead of a separate calcination process. Therefore, titania hollow microspheres with good spherical morphology are prepared which is more suitable for photocatalytic study.