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Stabilization of free radical intermediates on metal oxide semiconductors surfaces

Bahnemann, Detlef W. and Hoffmann, Michael R. (1988) Stabilization of free radical intermediates on metal oxide semiconductors surfaces. In: Electrochemical Society. Energy Technology Division. Electrochemical Society Proceedings. Vol.134. No.88-14. Electrochemical Society , Pennington, NJ, pp. 74-80. http://resolver.caltech.edu/CaltechAUTHORS:20150826-103411675

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Abstract

Free radicals intermediates are formed on the surface of metal oxide semiconductors, namely TiO_2 and Fe_2O_3, following the light-induced charge separation upon band-gap illumination. These radicals appear to adhere strongly to the surfaces of the small colloidal particles (diameters between 5 and 20 nm) employed in this study. A second electron-transfer step yielding the observed end-products therefore preceeds desorption of the reactive intermediates. Oxidation of methylviologen (1,1'-dimethyl-4,4'-bipyridylium chloride) and reduction of halothane (2-bromo-2-chloro-1,1,1- trifluoroethane) is thus found to proceed with high quantum yields and very specific mechanisms on colloidal TiO_2. The oxidation of sulfite on α-Fe_2O_3 particles yields the sulfite radical anion, SO_3^- , as initial intermediate. A subsequent electron transfer leading to the formation of sulfate occurs on the surface of the same catalyst particle.


Item Type:Book Section
ORCID:
AuthorORCID
Hoffmann, Michael R.0000-0002-0432-6564
Additional Information:© 1988 Electrochemical Society. The scientific collaboration with Ors. Ch.-H. Fischer and J. Mönig and Ms. J. Kern in different parts of this project has been stimulating and successful. DWB thanks the Hahn-Meitner-Institut for granting him a leave of absence.
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Deposited By: Ruth Sustaita
Deposited On:11 Sep 2015 22:32
Last Modified:11 Sep 2015 22:32

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