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Catalysts 2013, 3(2), 418-443; doi:10.3390/catal3020418

Generation of Free OHaq Radicals by Black Light Illumination of Degussa (Evonik) P25 TiO2 Aqueous Suspensions

1,*  and 2
1 Wallenius Water AB, Franzéngatan 3, SE-112 51 Stockholm, Sweden 2 KTH Chemical Science and Engineering, Applied Physical Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden
* Author to whom correspondence should be addressed.
Received: 16 December 2012 / Revised: 23 January 2013 / Accepted: 22 March 2013 / Published: 16 April 2013
(This article belongs to the Special Issue Photocatalysts)
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This work demonstrates how formation of strongly chemiluminescent 3-hydroxyphthalic hydrazide by hydroxylation of non-chemiluminescent phthalic hydrazide can be applied as a selective reaction probe to obtain information on authentic hydroxyl radical, i.e., OHaq, formation, in black light illuminated Degussa P25 TiO2 aerated suspensions in the pH range from 3 to 11. The OHaq formation was found to be strongly pH dependent. At alkaline pH, the apparent quantum efficiency of OHaq formation was estimated to be at the ~10−2 level whereas at acidic pH it was near zero. Addition of phosphate and fluoride ions substantially enhanced the OHaq production in the acidic pH range. It is suggested that OHaq-radical formation in TiO2 photocatalysis can occur by oxidation of hydroxyl ions in the water layer adsorbed on TiO2 surfaces.
Keywords: photocatalysis; TiO2; OHaq radical; chemiluminescence photocatalysis; TiO2; OHaq radical; chemiluminescence
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Liao, H.; Reitberger, T. Generation of Free OHaq Radicals by Black Light Illumination of Degussa (Evonik) P25 TiO2 Aqueous Suspensions. Catalysts 2013, 3, 418-443.

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