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Mapping of the Photoinduced Electron Traps in TiO₂ by Picosecond X-ray Absorption Spectroscopy

Lookup NU author(s): Professor Thomas Penfold

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Abstract

Titanium dioxide (TiO₂) is the most popular material for applications in solar-energy conversion and photocatalysis, both of which rely on the creation, transport, and trapping of charges (holes and electrons). The nature and lifetime of electron traps at room temperature have so far not been elucidated. Herein, we use picosecond X-ray absorption spectroscopy at the Ti K-edge and the Ru L₃-edge to address this issue for photoexcited bare and N719-dye-sensitized anatase and amorphous TiO₂ nanoparticles. Our results show that 100 ps after photoexcitation, the electrons are trapped deep in the defect-rich surface shell in the case of anatase TiO₂, whereas they are inside the bulk in the case of amorphous TiO₂. In the case of dye-sensitized anatase or amorphous TiO₂, the electrons are trapped at the outer surface. Only two traps were identified in all cases, with lifetimes in the range of nanoseconds to tens of nanoseconds.

Publication metadata

Author(s): Rittmann-Frank MH, Milne CJ, Rittmann J, Reinhard M, Penfold TJ, Chergui M

Publication type: Article

Publication status: Published

Journal: Angewandte Chemie International Edition

Year: 2014

Volume: 53

Issue: 23

Pages: 5858-5862

Print publication date: 02/06/2014

Online publication date: 12/05/2014

Acceptance date: 01/05/2014

ISSN (print): 1433-7851

ISSN (electronic): 1521-3773

Publisher: Wiley

URL: https://doi.org/10.1002/anie.201310522

DOI: 10.1002/anie.201310522

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