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

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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Abstract

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 3.0).
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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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