Photocatalytic Production of H_2O_2 and Organic Peroxides on Quantum-Sized Semiconductor Colloids
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).
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.Additional details
- Eprint ID
- 59399
- DOI
- 10.1021/es00054a006
- Resolver ID
- CaltechAUTHORS:20150811-111819148
- 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)
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2015-08-12Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field