Water- and oxygen-induced decay kinetics of photogenerated electrons in TiO2 and Pt/TiO2: A time-resolved infrared absorption study

Akira Yamakata, Taka Aki Ishibashi, Hiroshi Onishi

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278 Citations (Scopus)

Abstract

Electrons photogenerated in TiO2 and Pt/TiO2 catalysts were observed by time-resolved IR absorption spectroscopy. Transient IR absorption of an identical spectrum appeared on TiO2 and Pt/TiO2 irradiated by a 355 nm pump pulse. The absorption was attributed to optical transition of photogenerated electrons trapped in shallow midgap states. Electron- and hole-consuming reactions of adsorbates controlled the decay kinetics of the electrons competing with the electron-hole recombination. On TiO2, O2 from the gas-phase captured the electrons and accelerated the decay rate at a delay time of 10-100 μs. In water vapor, holes reacted with surface hydroxyls within 2 μs, and the recombination decay of the electrons was obstructed. When Pt/TiO2 was exposed to water, the oxidation and reduction steps of the water splitting reaction affected the decay kinetics in different time domains. Photogenerated holes oxidized water within 2 μs, whereas electrons reduced water at 10-900 μs.

Original languageEnglish
Pages (from-to)7258-7262
Number of pages5
JournalJournal of Physical Chemistry B
Volume105
Issue number30
DOIs
Publication statusPublished - Aug 2 2001
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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