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Characterization of oleophobic and photocatalytic TiO2 films prepared by surface functionalization with reactive SO2 gas
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
2011 (English)Conference paper, Published paper (Refereed)
Abstract [en]

We present an in situ Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) study of the photo-induced SO2 fixation on anatase TiO2 films. TiO2 films were prepared by DC magnetron sputtering and subsequently exposed to SO2 gas mixed in synthetic air. Simultaneous UV irradiation and SO2 exposure between 373 and 523 K resulted in significant SOx deposits on crystalline TiO2 films as determined by XPS, whereas amorphous films contained negligible amounts of SOx species. The oxidation state of sulfur successively changed from S4+ for SO2 adsorbed on crystalline TiO2 films at room temperature without irradiation to S6+ for films exposed to SO2 at elevated temperatures with simultaneous irradiation. With in situ FTIR the temporal evolution of the photo-induced surface reaction products formed on the TiO2 surfaces was monitored. It is shown that band gap excitation of TiO2 results in photo-induced oxidation of SO2 to form sulfite and sulfate species, which at elevated temperatures become coordinated to the TiO2 surface through interactions with O vacancies. These species makes the oxide surface acidic and is manifested in weak adherence of stearic acid (Fig. 1). The films show good stability as evidenced by sonication, repeated stearic acid and rinsing experiments. These results suggest that photo-induced surface treatment in reactive sulfur gases may be interesting for fabrication of oleophobic and anti-greasing coatings. Moreover, the SO2 modified shows excellent properties for sustained decomposition of acetaldehyde, a common indoor air pollutant. This is shown to be due to improved resistance towards site inhibition from carboxylate fragments which otherwise is known to impede the photocatalytic activity of TiO2 in gas-phase applications. Again this is attributed to a beneficial effect of the surface acid sites originating from the surface functionalization.

Place, publisher, year, edition, pages
2011.
National Category
Physical Chemistry Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
URN: urn:nbn:se:uu:diva-163080OAI: oai:DiVA.org:uu-163080DiVA: diva2:462655
Conference
JEP2011, 2nd European Conference on Photocatalysis, 29&30 Sep. 2011, Bordeaux, France
Funder
Swedish Research Council, 621-2010-3514
Available from: 2011-12-07 Created: 2011-12-07 Last updated: 2016-04-20

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Österlund, Lars

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