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Flux-Matching Conditions at TiO_2 Photoelectrodes: Is Interfacial Electron Transfer to O_2 Rate-Limiting in the TiO_2-Catalyzed Photochemical Degradation of Organics?

Kesselman, Janet M. and Shreve, Gary A. and Hoffmann, Michael R. and Lewis, Nathan S. (1994) Flux-Matching Conditions at TiO_2 Photoelectrodes: Is Interfacial Electron Transfer to O_2 Rate-Limiting in the TiO_2-Catalyzed Photochemical Degradation of Organics? Journal of Physical Chemistry, 98 (50). pp. 13385-13395. ISSN 0022-3654.

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A flux-matching condition has been applied to determine whether O_2 reduction is rate-limiting under photocatalytic conditions for the degradation of CHCl_3 at rutile TiO_2 single-crystal electrodes. In this approach, the potential dependence of the photooxidation current density is compared to the potential dependence of the current density for O_2 reduction. The potential at which the oxidation and reduction fluxes are equal determines the operating potential and the steady-state flux that will flow through the crystal under no applied bias. If this flux-matching condition occurs when the cathodic flux equals the flux of photogenerated carriers, then the predicted quantum yield should approach unity; otherwise, recombination should be significant in the TiO_2. Our measurements indicate that significant recombination will occur for the oxidation of typical organic molecules in H_2O over a range of pH values. The data also indicate that Pt catalysis of O_2 reduction should be beneficial for the oxidation of organic molecules, as would the use of alternate electron acceptors such as Fe(CN)_6^(3-). The O_2 reduction data and rotating disk electrode data collected in this work allow a quantitative comparison to theoretical estimates of the electron transfer rate constant for O_2 reduction at TiO_2. We also present an elucidation of the previously published theoretical treatments of TiO_2 charge transfer rate constants in view of the new data collected herein.

Item Type:Article
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Hoffmann, Michael R.0000-0001-6495-1946
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 1994 American Chemical Society. Received: July 6, 1994; In Final Form: September 16, 1994. We gratefully acknowledge ARPA (NAV 5 HFMN N0001 149211901) and the National Science Foundation, Grant CHE-9221311, for support of this work, and J.M.K. acknowledges the National Science Foundation for a predoctoral fellowship. We thank Dr. Com for a preprint of ref 51.
Funding AgencyGrant Number
Advanced Research Projects Agency (ARPA)UNSPECIFIED
NSF Predoctoral FellowshipUNSPECIFIED
Office of Naval Research (ONR)NAV 5 HFMN N0001 149211901
Issue or Number:50
Record Number:CaltechAUTHORS:20150810-083413352
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Official Citation:Flux-Matching Conditions at TiO2 Photoelectrodes: Is Interfacial Electron Transfer to O2 Rate-Limiting in the TiO2-Catalyzed Photochemical Degradation of Organics? Janet M. Kesselman, Gary A. Shreve, Michael R. Hoffmann, and Nathan S. Lewis The Journal of Physical Chemistry 1994 98 (50), 13385-13395 DOI: 10.1021/j100101a044
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59339
Deposited By: Ruth Sustaita
Deposited On:10 Aug 2015 22:39
Last Modified:03 Mar 2020 13:01

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