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Determination of catalytic properties of TiO2 coatings using aqueous solution of coumarin: Standardization efforts

Paper ID Volume ID Publish Year Pages File Format Full-Text
28957 44109 2009 9 PDF Available
Title
Determination of catalytic properties of TiO2 coatings using aqueous solution of coumarin: Standardization efforts
Abstract

Many types of supported photocatalytic TiO2 continue to be the subject of extensive development worldwide. Besides industrial production and practical use of the new photocatalytic materials, there is an increasing need for a simple and reliable procedure for characterization of photocatalytic activities of newly developed materials. The aim of our work was to develop a method for the determination of quantum yields of supported photocatalysts by employing an aqueous solution of a model organic compound and different thin TiO2 films. Additionally, also a newly defined parameter, the so-called mass efficiency, was introduced as an advantageous way of defining the photocatalytic activities. Coumarin (CM) was found to be an appropriate candidate for being a probe molecule when the photocatalytic degradation mainly occurs via the HO radical-mediated mechanism. An advantage of using CM is easy determination of highly fluorescent 7-hydroxycoumarin (7OHC). Different TiO2 films were deposited via sol–gel methods on soda-lime glass slides that were precovered with a thin SiO2 film, and via the sedimentation process from aqueous suspensions. Aqueous solutions of CM were irradiated using 365 nm radiation in the presence of titania films. Although Degussa P25 films showed approximately four times higher degradation rates compared to the sol–gel processed, its quantum yield was not more than 2.5 times higher. This could be explained by higher absorbance of Degussa P25 films per amount of the catalyst compared to sol–gel films. Since no information on the absorption characteristics of the material per unit of mass of the catalyst is included within the calculation of quantum yield, mass efficiency is suggested for the evaluation of photocatalytic properties of the coatings. It is evident from the present study that it is obligatory to evaluate the photocatalytic efficiencies of different area densities of the same photocatalyst in order to properly characterize the material's efficiency.

Keywords
7HOC, 7-hydroxycoumarin; CM, coumarin; Films C, sol–gel produced films with the addition of surfactant in the sol; Films D, sol–gel produced films without the addition of surfactant in the sol; Films P, Degussa P25 films; FLD, fluorescence detector; RSD,
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Determination of catalytic properties of TiO2 coatings using aqueous solution of coumarin: Standardization efforts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 201, Issues 2–3, 25 January 2009, Pages 142–150
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us