Abstract
Changes in pH have been used to shift the band-edge positions of n-type ZnO electrodes relative to solution-based electron acceptors having pH-independent redox potentials. Differential capacitance vs. potential and current density vs. potential measurements using [Co(bpy)3]3+/2+ and [Ru(bpy)2(MeIm)2]3+/2+ (where bpy = 2,2′-bipyridyl and MeIm = 1-methyl-imidazole) allowed investigation of the pH-induced driving-force dependence of the interfacial electron-transfer rate in the normal and inverted regions of electron transfer, respectively. All rate processes were observed to be kinetically first-order in the concentration of electrons at the ZnO surface and first-order in the concentration of dissolved redox acceptors. Measurements using [Co(bpy)3]3+/2+, which has a low driving force and a high reorganization energy in contact with ZnO electrodes, and measurements of [Ru(bpy)2(MeIm)2]3+/2+, which has a high driving force and a low reorganization energy in contact with ZnO electrodes, allowed for the evaluation of both the normal and inverted regions of interfacial electron-transfer processes, respectively. The rate constant at optimum exoergicity was observed to be approximately 5 × 10-17 cm4 s-1. The rate constant vs. driving-force dependence at n-type ZnO electrodes exhibited both normal and inverted regions, and the data were well-fitted by parabolas generated using classical electron-transfer theory.
| Original language | English |
|---|---|
| Pages (from-to) | 15-23 |
| Number of pages | 9 |
| Journal | Chemical Physics |
| Volume | 326 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - Jul 11 2006 |
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Keywords
- Electron transfer
- pH
- Semiconductor
- ZnO
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Spectroscopy
- Atomic and Molecular Physics, and Optics
Cite this
Measurement of the driving force dependence of interfacial charge-transfer rate constants in response to pH changes at n-ZnO/H2O interfaces. / Hamann, Thomas W.; Gstrein, Florian; Brunschwig, Bruce S.; Lewis, Nathan S.
In: Chemical Physics, Vol. 326, No. 1, 11.07.2006, p. 15-23.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Measurement of the driving force dependence of interfacial charge-transfer rate constants in response to pH changes at n-ZnO/H2O interfaces
AU - Hamann, Thomas W.
AU - Gstrein, Florian
AU - Brunschwig, Bruce S.
AU - Lewis, Nathan S
PY - 2006/7/11
Y1 - 2006/7/11
N2 - Changes in pH have been used to shift the band-edge positions of n-type ZnO electrodes relative to solution-based electron acceptors having pH-independent redox potentials. Differential capacitance vs. potential and current density vs. potential measurements using [Co(bpy)3]3+/2+ and [Ru(bpy)2(MeIm)2]3+/2+ (where bpy = 2,2′-bipyridyl and MeIm = 1-methyl-imidazole) allowed investigation of the pH-induced driving-force dependence of the interfacial electron-transfer rate in the normal and inverted regions of electron transfer, respectively. All rate processes were observed to be kinetically first-order in the concentration of electrons at the ZnO surface and first-order in the concentration of dissolved redox acceptors. Measurements using [Co(bpy)3]3+/2+, which has a low driving force and a high reorganization energy in contact with ZnO electrodes, and measurements of [Ru(bpy)2(MeIm)2]3+/2+, which has a high driving force and a low reorganization energy in contact with ZnO electrodes, allowed for the evaluation of both the normal and inverted regions of interfacial electron-transfer processes, respectively. The rate constant at optimum exoergicity was observed to be approximately 5 × 10-17 cm4 s-1. The rate constant vs. driving-force dependence at n-type ZnO electrodes exhibited both normal and inverted regions, and the data were well-fitted by parabolas generated using classical electron-transfer theory.
AB - Changes in pH have been used to shift the band-edge positions of n-type ZnO electrodes relative to solution-based electron acceptors having pH-independent redox potentials. Differential capacitance vs. potential and current density vs. potential measurements using [Co(bpy)3]3+/2+ and [Ru(bpy)2(MeIm)2]3+/2+ (where bpy = 2,2′-bipyridyl and MeIm = 1-methyl-imidazole) allowed investigation of the pH-induced driving-force dependence of the interfacial electron-transfer rate in the normal and inverted regions of electron transfer, respectively. All rate processes were observed to be kinetically first-order in the concentration of electrons at the ZnO surface and first-order in the concentration of dissolved redox acceptors. Measurements using [Co(bpy)3]3+/2+, which has a low driving force and a high reorganization energy in contact with ZnO electrodes, and measurements of [Ru(bpy)2(MeIm)2]3+/2+, which has a high driving force and a low reorganization energy in contact with ZnO electrodes, allowed for the evaluation of both the normal and inverted regions of interfacial electron-transfer processes, respectively. The rate constant at optimum exoergicity was observed to be approximately 5 × 10-17 cm4 s-1. The rate constant vs. driving-force dependence at n-type ZnO electrodes exhibited both normal and inverted regions, and the data were well-fitted by parabolas generated using classical electron-transfer theory.
KW - Electron transfer
KW - pH
KW - Semiconductor
KW - ZnO
UR - http://www.scopus.com/inward/record.url?scp=33745490076&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33745490076&partnerID=8YFLogxK
U2 - 10.1016/j.chemphys.2006.02.027
DO - 10.1016/j.chemphys.2006.02.027
M3 - Article
VL - 326
SP - 15
EP - 23
JO - Chemical Physics
JF - Chemical Physics
SN - 0301-0104
IS - 1
ER -