Photocatalytic property of SiO2 TiO2 nanoparticles prepared by sol-hydrothermal process

In the present work, the effect of the composition of the solvent, the embedded silica content and the concentration of acid on the particle size and crystal structure of the solhydrothermal desired titania particles are investigated. The structural, morphological and photocatalytic properties of the synthesized SiO2/TiO2 are characterized by XRD, TEM, Raman and UV-Visible spectroscopy.
Hydrothermal synthesis is a promising method to obtain nanocrystalline titania particles since crystalline product can be obtained at relatively low reaction temperature (<250◦C). The crystal structure, particle size and morphology can easily be controlled by changing hydrothermal condition such as temperature, pH, solvent composition, reactant concentration, additive, etc.
J Electroceram (2006) 17:899–902 DOI 10.1007/s10832-006-9071-5
Photocatalytic property of SiO2/TiO2 nanoparticles prepared by sol-hydrothermal process
E. Y. Kim · C. M. Whang · W. I. Lee · Y. H. Kim
Addition of silica to TiO2 brought about an increase in the photocatalytic activity by suppressing the phase transition from anatase to rutile. Judging from the result of the decomposition of 1, 4-dichlorobenzene, the most efficient catalyst was found to be 0.2 mole fraction SiO2 embedded TiO2 prepared with ethanol-rich solvent (the volume ratio of ethanol to water is 4).
TTIP and TEOS precursors were dissolved separately in ethanol whose total volume was adjusting to give the desired titania and silica mole ratio. Then, the prepared solutions were mixed and added to the acidic water. The final mixed sol was remained clear. The clear solution was transferred into a glass-lined autoclave, and left to react at 250◦C for 2 hour. After hydrothermal reaction, the crystallized nanoparticles were obtained as a colloidal suspension. To obtain powdered samples the suspensions were dried in oven at 50◦C, and final drying resulted in fine white powder of SiO2/TiO2 nanoparticles.
The major phase and crystallite size of the obtained particles was analyzed by X-ray diffractometer (XRD, Rigaku DMAX 2500) using Cu-Kα radiation. The morphology and grain size of the samples were examined using transmission electron microscopy (TEM, Philips CM200). Raman spectra of the samples were obtained with FT- Raman spectroscopy (Bruker Co. RFS100/S). The average diameter of agglomerated SiO2/TiO2 nanoparticles in suspended aqueous solution was determined by a particle size analyzer (Otsuka ELS-8000).
Received: 27 June 2005 / Revised: 20 March 2006 / Accepted: 9 May 2006 C Springer Science + Business Media, LLC 2006
Abstract Silica-embedded nanocrystalline TiO2 powders were synthesized by sol-hydrothermal process. The influence of the composition of the solvent and the embedded silica content on the phase transition, grain growth and subsequently, on the photoactivity of TiO2 were investigated. The volume ratio of ethanol to water for the solvent composition was varied from 0.125 to 8 and the mole fraction of silica content was changed from 0 to 0.4, while the condition for hydrothermal reaction was fixed at 250◦C for 2 hour. With an increase in ethanol content in solvent composition, the crystallite sizes of pure TiO2 particles decreased from 15 nm to 6 nm and crystal phase changed from rutile/anatase mixed phase to pure anatase phase.
W. I. Lee · Y. H. Kim Dept. of Chemistry, Inha University, Incheon 402-751, Korea
Titanium tetraisopropoxide (TTIP) and tetraethylorthosilicate (TEOS) were used as precursors for titania and silica, respectively. Ethanol and water were employed as solvents and nitric acid was used as a catalyst to stabilize the sol. Appropriate amount of TTIP and TEOS precursors were taken to give the required silica: titania mole ratio. The mole fraction
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J Electroceram (2006) 17:899–902
of silica was changed from 0 to 0.4. The volume ratio between ethanol to water for solvent composition was varied from 0.125 to 8 making total of 90 ml of mixed ethanol and water solution. Nitric acid was added to the water until the pH of the acidic water reached 0.3. In order to see the effect of acid concentration on the crystal structure, we also prepared acidic water whose pH is 0.6.
2 Experimental
E. Y. Kim · C. M. Whang ( ) School of Materials Science and Engineering, Inha University, Incheon 402-751, Korea e-mail: cmwhang@inha.ac.kr