Effects of Precipitation, SolGel Synthesis Conditions, and Drying Methods on the Properties of Nano‐TiO2 for Photocatalysis Applications

Abstract

AbstractA comparative study of TiO2 powders prepared by precipitation and sol–gel methods was conducted. Titanium tetrachloride and titanium tetraisopropoxide were used as the starting materials for the precipitation and sol–gel processes, respectively. The effects of the two different drying methods, freeze drying and normal drying at 100 °C, of the precipitates on the properties of the prepared TiO2 powders were also investigated. The effects of the synthesis methods on phase, surface area, crystallite size, and photodegradation of methylene blue were studied by XRD, SEM, TEM, BET, and UV/Vis techniques. It was found that the major phase of the synthesized TiO2 was anatase, but small amounts of the brookite phase (<10 %) were found in some samples. The synthesized anatase TiO2 with no pretreatment was found to be stable up to 600 °C for the samples prepared by the precipitation method, whereas a small amount of rutile was detected for the sample prepared by the sol–gel method when heated to 600 °C. Effects of the different processing methods on phase, particle size, surface area, and photocatalytic activity were not highly pronounced. However, the calcination temperature was found to have a strong influences on the properties. As the calcination temperature increased, the size of the crystallite and the percent degradation of methylene blue were found to increase, whereas the surface area was found to decrease. These results indicate the degree of crystallinity has a greater effect on the photocatalytic activity than the surface area for nano‐TiO2 synthesized by these methods.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)