Electron-hole recombination time at TiO2 single-crystal surfaces: Influence of surface band bending

Kenichi Ozawa, Masato Emori, Susumu Yamamoto, Ryu Yukawa, Shingo Yamamoto, Rei Hobara, Kazushi Fujikawa, Hiroshi Sakama, Iwao Matsuda

Research output: Contribution to journalArticlepeer-review

209 Citations (Scopus)


Photocatalytic activity is determined by the transport property of photoexcited carriers from the interior to the surface of photocatalysts. Because the carrier dynamics is influenced by a space charge layer (SCL) in the subsurface region, an understanding of the effect of the potential barrier of the SCL on the carrier behavior is essential. Here we have investigated the relaxation time of the photoexcited carriers on single-crystal anatase and rutile TiO2 surfaces by time-resolved photoelectron spectroscopy and found that carrier recombination, taking a nanosecond time scale at room temperature, is strongly influenced by the barrier height of the SCL. Under the flat-band condition, which is realized in nanometer-sized photocatalysts, the carriers have a longer lifetime on the anatase surface than the rutile one, naturally explaining the higher photocatalytic activity for anatase than rutile.

Original languageEnglish
Pages (from-to)1953-1957
Number of pages5
JournalJournal of Physical Chemistry Letters
Issue number11
Publication statusPublished - 2014 Jun 5


  • anatase
  • carrier lifetime
  • photocatalysis
  • rutile
  • space charge layer
  • time-resolved photoelectron spectroscopy


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