Microstructure and Photocatalytic Property of SiO2-TiO2 under Various Process Conditions

초록

The purpose of this study is to synthesize TiO2 photocatalyst which is highly effective in decomposing volatile organic compounds. In this work, the crystallnity, rutile/anatase ratio, particle size of TiO2, and reactive surface area is controlled by varying the SiO2 content, calcination temperature and different synthetic procedure. XRD, SEM, BET and UV/Visible spectroscopy studies probe the microstructure and photocatalytic characteristics of the synthesized SiO2-TiO2 powders, and the optimum cinditions to get the most active powders are determined. Titanium isopropoxide and tetraethylorthosilicate are used as precursors of titania and silica, respectively. Isopropanol and ethanol are employed as solvents, and nitric acid is used as a catalyst. xSiO2-(1-x)TiO2 (x=0.1, 0.2, 0.3, 0.4), powder is prepared with various sintering temperature with sol-gel and hydrothermal process. It is confirmed that the silica-titania mixture has high thermal stability, which results in the suppression of phase transformation of titania from anatase to rutile. As ths silica content increases from 0.1 to 0.4 mole ratio, the crystallite size decreases from 11.23 to 7.29 nm. This result confirms that embedding amorthous SiO2 into titania inhibits the growth of anatase crystal of titania particles to a certain extent. All the XRD patterns of titania powders synthesized at 250℃ by hydrothermal process can be assigned to anatase, and the decrease in crystallite size from 12.36 to 9.44 nm with the increase in surface area is observed. The dichlorobenzene (DCB) decomposition rate for sol-gel derived SiO2-TiO2 powders prepared at 750℃ increase as silica content increases. The photoactivity of powder with 30 mole % silica is higher than Degussa-P25, and however, the powders prepared at 250℃ by hydrothermal process have lower DCB decomposition rate than Degussa-P25 due to the low surface area and low crystallnity.