Accession Number:

ADA301441

Title:

Semiconductor Based Interfacial Electron Transfer Reactivity: Decoupling Kinetics from pH Dependent Band Energetics in a Dye-Sensitized Titanium Dioxide/Aqueous Solution System.

Descriptive Note:

Technical rept.,

Corporate Author:

NORTHWESTERN UNIV EVANSTON IL DEPT OF CHEMISTRY

Personal Author(s):

Report Date:

1995-10-26

Pagination or Media Count:

17.0

Abstract:

Hexaphosphonation of Rubpy32 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 E sub CB. Evaluation of the fast component yields a back electron transfer rate constant of 5 or - 0.5 x 10exp 8s that is invariant between pH 11 and H sub o -8, despite a greater than 1 eV change in E sub CB 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. jg p.2

Subject Categories:

  • Inorganic Chemistry
  • Physical Chemistry
  • Atomic and Molecular Physics and Spectroscopy
  • Solid State Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE