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Measurement of the Free-Energy Dependence of Interfacial Charge-Transfer Rate Constants using ZnO/H_2O Semiconductor/Liquid Contacts

Hamann, Thomas W. and Gstrein, Florian and Brunschwig, Bruce S. and Lewis, Nathan S. (2005) Measurement of the Free-Energy Dependence of Interfacial Charge-Transfer Rate Constants using ZnO/H_2O Semiconductor/Liquid Contacts. Journal of the American Chemical Society, 127 (21). pp. 7815-7824. ISSN 0002-7863. doi:10.1021/ja0436188.

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The dependence of electron-transfer rate constants on the driving force for interfacial charge transfer has been investigated using n-type ZnO electrodes in aqueous solutions. Differential capacitance versus potential and current density versus potential measurements were used to determine the energetics and kinetics, respectively, of the interfacial electron-transfer processes. A series of nonadsorbing, one-electron, outer-sphere redox couples with formal reduction potentials that spanned approximately 900 mV allowed evaluation of both the normal and Marcus inverted regions of interfacial electron-transfer processes. All rate processes were observed to be kinetically first-order in the concentration of surface electrons and first-order in the concentration of dissolved redox acceptors. The band-edge positions of the ZnO were essentially independent of the Nernstian potential of the solution over the range 0.106−1.001 V vs SCE. The rate constant at optimal exoergicity was observed to be approximately 10^(-16) cm4 s^(-1). The rate constant versus driving force dependence at n-type ZnO electrodes exhibited both normal and inverted regions, and the data were well-fit by a parabola generated using classical Marcus theory with a reorganization energy of 0.67 eV. NMR line broadening measurements of the self-exchange rate constants indicated that the redox couples had reorganization energies of 0.64−0.69 eV. The agreement between the reorganization energy of the ions in solution and the reorganization energy for the interfacial electron-transfer processes indicated that the reorganization energy was dominated by the redox species in the electrolyte, as expected from an application of Marcus theory to semiconductor electrodes.

Item Type:Article
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URLURL TypeDescription Information
Brunschwig, Bruce S.0000-0002-6135-6727
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2005 American Chemical Society. Received October 20, 2004. Publication Date (Web): May 7, 2005. We acknowledge the Department of Energy, Office of Basic Energy Sciences, for support of this work. Dr. Mona Shahgholi provided helpful assistance in acquiring mass spectroscopic data, and Drs. Nagarajan Srivatsan and Norman Sutin are acknowledged for helpful conversations.
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Department of Energy (DOE)UNSPECIFIED
Issue or Number:21
Record Number:CaltechAUTHORS:20170425-161159177
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Official Citation:Measurement of the Free-Energy Dependence of Interfacial Charge-Transfer Rate Constants using ZnO/H2O Semiconductor/Liquid Contacts Thomas W. Hamann, Florian Gstrein, Bruce S. Brunschwig, and Nathan S. Lewis Journal of the American Chemical Society 2005 127 (21), 7815-7824 DOI: 10.1021/ja0436188
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76925
Deposited By: Tony Diaz
Deposited On:26 Apr 2017 01:37
Last Modified:15 Nov 2021 17:03

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