Semiconductor-based interfacial electron-transfer reactivity: Decoupling kinetics from pH-dependent band energetics in a dye-sensitized titanium dioxide/aqueous solution system

Susan G. Yan, Joseph T Hupp

Research output: Contribution to journalArticle

182 Citations (Scopus)

Abstract

Hexaphosphonation of Ru(bpy)32+ provides a basis for surface attachment to nanocrystalline TiO2 in film (electrode) or colloidal form and for subsequent retention of the molecule over an extraordinarily wide pH range. Visible excitation of the surface-attached complex leads to rapid injection of an electron into the semiconductor. Return electron transfer, monitored by transient absorbance spectroscopy, is biphasic with a slow component that can be reversibly eliminated by adjusting the potential of the dark electrode to a value close to the conduction-band edge (ECB). Evaluation of the fast component yields a back-electron-transfer rate constant of 5(±0.5) × 107 s-1 that is invariant between pH = 11 and H0 = -8, despite a greater than 1 eV change in ECB (i.e., the nominal free energy of the electron in the electrode). The observed insensitivity to large changes in band-edge energetics stands in marked contrast to the behavior expected from a straightforward application of conventional interfacial electron-transfer theory and calls into question the existing interpretation of these types of reactions as simple inverted region processes.

Original languageEnglish
JournalJournal of Physical Chemistry
Volume100
Issue number17
Publication statusPublished - Apr 25 1996

Fingerprint

titanium oxides
decoupling
Titanium dioxide
electron transfer
Coloring Agents
Dyes
reactivity
dyes
Semiconductor materials
aqueous solutions
Kinetics
electrodes
Electrons
kinetics
Electrodes
attachment
conduction bands
electrons
adjusting
free energy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

@article{04649326808e465582ed7dea772862f0,
title = "Semiconductor-based interfacial electron-transfer reactivity: Decoupling kinetics from pH-dependent band energetics in a dye-sensitized titanium dioxide/aqueous solution system",
abstract = "Hexaphosphonation of Ru(bpy)32+ provides a basis for surface attachment to nanocrystalline TiO2 in film (electrode) or colloidal form and for subsequent retention of the molecule over an extraordinarily wide pH range. Visible excitation of the surface-attached complex leads to rapid injection of an electron into the semiconductor. Return electron transfer, monitored by transient absorbance spectroscopy, is biphasic with a slow component that can be reversibly eliminated by adjusting the potential of the dark electrode to a value close to the conduction-band edge (ECB). Evaluation of the fast component yields a back-electron-transfer rate constant of 5(±0.5) × 107 s-1 that is invariant between pH = 11 and H0 = -8, despite a greater than 1 eV change in ECB (i.e., the nominal free energy of the electron in the electrode). The observed insensitivity to large changes in band-edge energetics stands in marked contrast to the behavior expected from a straightforward application of conventional interfacial electron-transfer theory and calls into question the existing interpretation of these types of reactions as simple inverted region processes.",
author = "Yan, {Susan G.} and Hupp, {Joseph T}",
year = "1996",
month = "4",
day = "25",
language = "English",
volume = "100",
journal = "Journal of Physical Chemistry",
issn = "0022-3654",
publisher = "American Chemical Society",
number = "17",

}

TY - JOUR

T1 - Semiconductor-based interfacial electron-transfer reactivity

T2 - Decoupling kinetics from pH-dependent band energetics in a dye-sensitized titanium dioxide/aqueous solution system

AU - Yan, Susan G.

AU - Hupp, Joseph T

PY - 1996/4/25

Y1 - 1996/4/25

N2 - Hexaphosphonation of Ru(bpy)32+ provides a basis for surface attachment to nanocrystalline TiO2 in film (electrode) or colloidal form and for subsequent retention of the molecule over an extraordinarily wide pH range. Visible excitation of the surface-attached complex leads to rapid injection of an electron into the semiconductor. Return electron transfer, monitored by transient absorbance spectroscopy, is biphasic with a slow component that can be reversibly eliminated by adjusting the potential of the dark electrode to a value close to the conduction-band edge (ECB). Evaluation of the fast component yields a back-electron-transfer rate constant of 5(±0.5) × 107 s-1 that is invariant between pH = 11 and H0 = -8, despite a greater than 1 eV change in ECB (i.e., the nominal free energy of the electron in the electrode). The observed insensitivity to large changes in band-edge energetics stands in marked contrast to the behavior expected from a straightforward application of conventional interfacial electron-transfer theory and calls into question the existing interpretation of these types of reactions as simple inverted region processes.

AB - Hexaphosphonation of Ru(bpy)32+ provides a basis for surface attachment to nanocrystalline TiO2 in film (electrode) or colloidal form and for subsequent retention of the molecule over an extraordinarily wide pH range. Visible excitation of the surface-attached complex leads to rapid injection of an electron into the semiconductor. Return electron transfer, monitored by transient absorbance spectroscopy, is biphasic with a slow component that can be reversibly eliminated by adjusting the potential of the dark electrode to a value close to the conduction-band edge (ECB). Evaluation of the fast component yields a back-electron-transfer rate constant of 5(±0.5) × 107 s-1 that is invariant between pH = 11 and H0 = -8, despite a greater than 1 eV change in ECB (i.e., the nominal free energy of the electron in the electrode). The observed insensitivity to large changes in band-edge energetics stands in marked contrast to the behavior expected from a straightforward application of conventional interfacial electron-transfer theory and calls into question the existing interpretation of these types of reactions as simple inverted region processes.

UR - http://www.scopus.com/inward/record.url?scp=33748606923&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33748606923&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:33748606923

VL - 100

JO - Journal of Physical Chemistry

JF - Journal of Physical Chemistry

SN - 0022-3654

IS - 17

ER -