The effect of calcination temperature on the surface microstructure and photocatalytic activity of TiO₂ thin films prepared by liquid phase deposition

Jia-Guo YU, Huo-Gen YU, Bei CHENG, Xiu-Jian ZHAO, Jimmy C. YU, Wing Kei HO

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Abstract

TiO₂ thin films were prepared on fused quartz by the liquid-phase deposition (LPD) method from a (NH₄)₂TiF₆ aqueous solution upon addition of boric acid (H₃BO₃) and calcined at various temperatures. The as-prepared films were characterized with thermogravimetry (TG), Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), UV−Visible spectrophotometry (UV−Vis), scanning electron microscopy (SEM), photoluminescence spectra (PL), and X-ray photoelectron spectroscopy (XPS), respectively. The photocatalytic activity of the samples was evaluated by photocatalytic decolorization of methyl orange aqueous solution. It was found that the as-prepared TiO₂ thin films contained not only Ti and O elements, but also a small amount of F, N, and Si elements. The F and N came from the precursor solution, and the amount of F decreased with increasing calcination temperature. Two sources of Si were identified. One was from the SiF₆²⁻ ions, which were formed by a reaction between the treatment solution and quartz substrate. The other was attributed to the diffusion of Si from the surface of quartz substrate into TiO₂ thin film at 700 °C or higher calcination temperatures. With increasing calcination temperature, the photocatalytic activity of the TiO₂ thin films gradually increased due to the improvement of crystallization of the anatase TiO₂ thin films. At 700 °C, the TiO₂ thin film showed the highest photocatalytic activity due to the increasing amount of SiO₂ as an adsorbent center and better crystallization of TiO₂ in the composite thin film. Moreover, the SiO₂/TiO₂ composite thin film showed the lowest PL intensity due to a decrease in the recombination rate of photogenerated electrons and holes under UV light irradiation, which further confirms the film with the highest photocatalytic activity at 700 °C. When the calcination temperature is higher than 700 °C, the decrease in photocatalytic activity is due to the formation of rutile and the sintering and growth of TiO₂ crystallites resulting in the decrease of surface area. Copyright © 2003 American Chemical Society.
Original languageEnglish
Pages (from-to)13871-13879
JournalJournal of Physical Chemistry B
Volume107
Issue number50
DOIs
Publication statusPublished - Nov 2003

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Citation

Yu, J.-G., Yu, H.-G., Cheng, B., Zhao, X.-J., Yu, J. C., & Ho, W.-K. (2003). The effect of calcination temperature on the surface microstructure and photocatalytic activity of TiO₂ thin films prepared by liquid phase deposition. Journal of Physical Chemistry B, 107(50), 13871-13879. doi: 10.1021/jp036158y