The Fabrication And Photocatalytic Activity Of Nano-TiO₂Hollow Spheres

Titania hollow spheres with nanometer size were prepared by template methodemploying polystyrene (PS) as template and tetrabutyl titanate (TBOT) as titaniumsource. The titania hollow spheres were characterized with XRD, FESEM, TEM, BET.The photocatalytic activity of titania hollow spheres was evaluated by UV-Visabsorption spectra and degredation of benzene under UV irradiation. The main resultsare as follows:1. PS nanoshperes were synthesized by emulsifier-free emulsion polymerization.Reacted at70°C for18h, we can abtain monodisperse PS nanospheres withelectronegative surface and homogeneous size. The size of PS nanospheres decreasedas the decrease of the concentration of styrene monomer and the gain of theconcentration of K2S2O8.2. Titania hollow spheres were prepared at different calcining temperature tostudy the effect of caicining temperature on the hollow spheres. The results showedthat as the calcining temperature increased the phase of hollow spheres changed fromanatase to rutile. Calcined under700°C, the product of pure anatase crystallinityincreases with the increasing of temperature. Calcined above700°C, the rutile titaniaappeared and the rate of rutile phase increased quickly as the temperature increased.The titania hollow spheres abtained at700°C had good crystallinity and morphology,therefore it showed greatest photocatalytic activity. The degredation of benzenereached85%after80min, which is about1.3times to that of P25.3. The effect of the amount of ammonia added on the hollow spheres was studied.The results showed the amount of ammonia had great effect on the morphology of theproducts. Without addition of ammonia, we could not get hollow spheres, so thesample showed poor photocatalytic activity. Excessive amount of ammonia wouldquicken the hydrolysis rate of TBOT, which result in the change of the morphology ofhollow spheres, leading to low photocatalytic activity of the samples. The samplewith0.5ml ammonia had good morphology and showed the best photocatalyticactivity. The benzene was totally decomposed after80min.4. The effect of the amount of TBOT on the titania hollow spheres was investigated. The results showed the amount of TBOT had great effect on thethickness of the shell of the hollow spheres. The sample with3g TBOT had theappropriate thickness, resulting in good photocatalytic activity.5. The effect of the size of PS nanospheres on titania hollow spheres was studied.The photocatalytic activity of hollow spheres increased gradually with the decrease ofthe size of PS nanospheres. The sample prepared by PS with a diameter of300nmshowed the best photocatalytic activity, which was about1.6times to P25.