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Photocatalytic Oxidation of Organic Compounds and Reduction of Dioxygen with Quantum-Sized Semiconductors

Hoffman, A. J. and Hoffmann, M. R. (1993) Photocatalytic Oxidation of Organic Compounds and Reduction of Dioxygen with Quantum-Sized Semiconductors. In: Photocatalylic Purification and Treatment of Water and Air. Trace Metals in the Environment. No.3. Elsevier , Amsterdan, pp. 155-162. ISBN 0-444-89855-7.

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Aqueous, oxygenated suspensions of quantum-sized ZnO particles with added hole scavengers are shown to produce steady-state hydrogen peroxide concentrations as high as 2 mM upon bandgap irradiation. Quantum yields for H_2O_2 as high as 30% are observed at the lowest illumination intensities. The quantum yield is shown to follow an inverse square-root dependency on absorbed light intensity. The initial rate of H_2O_2 production is 100 to 1000 times faster with Q-sized particles (4-5 run) than with bulk ZnO particles (10-1000 μm). Maximum hydrogen peroxide concentrations are observed only with added hole scavengers. The order of efficiency of hole scavengers is: formate > oxalate > acetate > water > citrate. H_2O_2 formation results from the reaction of conduction band electrons with adsorbed oxygen. Observed reactions products other than H_2O_2 are consistent with oxidation of the hole scavenger by hydroxyl radicals which are produced by reaction of the bole with surface hydroxyl species (□-ZnOH; i.e., a trapped hole) or with water.

Item Type:Book Section
Hoffmann, M. R.0000-0001-6495-1946
Additional Information:© 1993 Elsevier Science Publishers B.V. We are grateful to the US EPA for financial support, and we appreciate the assistance of Drs. Detlef Bahnemann, G. Mills and Claudius Kormann in the early stages of this research.
Funding AgencyGrant Number
Environmental Protection Agency (EPA)UNSPECIFIED
Series Name:Trace Metals in the Environment
Issue or Number:3
Record Number:CaltechAUTHORS:20150825-154505449
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59896
Deposited By: Ruth Sustaita
Deposited On:26 Aug 2015 15:54
Last Modified:03 Mar 2020 13:01

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