Electronic structure and photoelectrochemical properties of an Ir-doped SrTiO3 photocatalyst

Seiji Kawasaki, Ryota Takahashi, Kazuto Akagi, Jun Yoshinobu, Fumio Komori, Koji Horiba, Hiroshi Kumigashira, Katsuya Iwashina, Akihiko Kudo, Mikk Lippmaa

Research output: Contribution to journalArticlepeer-review

44 Citations (Scopus)

Abstract

The effect of iridium valence in Ir:SrTiO3 on the electronic structure and the photocatalytic activity in a water splitting reaction was studied. Epitaxial thin film photoelectrodes were grown with controlled Ir valence and used to measure the electrochemical efficiency of Ir:SrTiO3. The positions of the in-gap Ir impurity levels were determined by optical and X-ray photoelectron spectroscopies. Comparison with ab initio calculations was used to assign the observed electronic states to either Ir4+ or Ir3+ dopants in SrTiO3. The measurements show that Ir3+:SrTiO3 forms a single midgap impurity state that is strongly localized, completely quenching the photoelectrochemical response. An anodic photoresponse was seen in Ir4+:SrTiO3 under visible-light illumination up to a wavelength of 600 nm (hν = 2.0 eV). Ir4+:SrTiO3 contains an in-gap state close to the top of the SrTiO3 valence band. The performance of Ir4+:SrTiO3 in electrochemical reactions is compared with cathodic Rh3+:SrTiO3, clearly illustrating the importance of strong dopant d-electron hybridization with the oxygen 2p valence band of SrTiO3 for improving the energy conversion efficiency in SrTiO3-based photocatalysts.

Original languageEnglish
Pages (from-to)20222-20228
Number of pages7
JournalJournal of Physical Chemistry C
Volume118
Issue number35
DOIs
Publication statusPublished - 2014 Sep 4

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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