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Photocatalytic Production of H_2O_2 and Organic Peroxides on Quantum-Sized Semiconductor Colloids

Hoffman, Amy J. and Carraway, Elizabeth R. and Hoffmann, Michael R. (1994) Photocatalytic Production of H_2O_2 and Organic Peroxides on Quantum-Sized Semiconductor Colloids. Environmental Science and Technology, 28 (5). pp. 776-785. ISSN 0013-936X. https://resolver.caltech.edu/CaltechAUTHORS:20150811-111819148

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Abstract

Illuminated (320 ≤ X ≤ 370 nm), aqueous suspensions of transparent quantum-sized (Q-sized) ZnO semiconductor colloids in the presence of carboxylic acids and oxygen are shown to produce steady-state concentrations of H_2O_2 as high as 2 mM. Maximum H_2O_2 concentrations are observed only with added electron donors (i.e., hole scavengers). The order of efficiency of hole scavengers is as follows: formate > oxalate > acetate > citrate. Isotopic labeling experiments with ^(18)O_2 are consistent with the hypothesis that hydrogen peroxide is produced directly by the reduction of adsorbed oxygen by conduction band electrons. Quantum yields for H_2O_2 production are near 30% at low photon fluxes. However, the quantum yield is shown to vary with the inverse square root of absorbed light intensity [Φ ∝ ((I_(abs))^(-1)½)], with the wavelength of excitation, and with the diameter of the Q-sized colloids. The initial rate of H_2O_2 production is 100-1000 times faster with Q-sized ZnO particles (D_p = 4-5 nm) than with bulk-sized ZnO particles (D_p = 0.1 µm).


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/es00054a006DOIArticle
http://pubs.acs.org/doi/abs/10.1021/es00054a006PublisherArticle
ORCID:
AuthorORCID
Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 1994 American Chemical Society. Received for review May 12,1993. Revised manuscript received November 29,1993. Accepted January 5, 1994. We are grateful to the EPA (815041-01-0; 815170-01-0) and ARPA (NAV5 HFMN N0001492J1901) for financial support, and we appreciate the assistance of Drs. Detlef Bahnemann, Claudius Kormann, and Peter Green in various aspects of this research.
Funders:
Funding AgencyGrant Number
Environmental Protection Agency (EPA)815041-01-0
Environmental Protection Agency (EPA)815170-01-0
Office of Naval Research (ONR)NAV5 HFMN N0001492J1901
Advanced Research Projects Agency (ARPA)UNSPECIFIED
Issue or Number:5
Record Number:CaltechAUTHORS:20150811-111819148
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150811-111819148
Official Citation:Photocatalytic Production of H2O2 and Organic Peroxides on Quantum-Sized Semiconductor Colloids Amy J. Hoffman, Elizabeth R. Carraway, and Michael R. Hoffmann Environmental Science & Technology 1994 28 (5), 776-785 DOI: 10.1021/es00054a006
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59399
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:12 Aug 2015 16:37
Last Modified:03 Mar 2020 13:01

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