Enhanced Visible Light Response of TiO2 Codoped with Cr and Ta Photocatalysts by Electron Doping

Fumiaki Amano, Masashi Nakata, Junie Jhon M. Vequizo, Akira Yamakata

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

The importance of electron concentration in rutile TiO2 photocatalysts motivated us to apply H2 reduction treatment to visible-light-responsive TiO2 photocatalysts sensitized by chromium ion doping. We found that H2 reduction treatment of rutile TiO2 particles codoped with Ta and Cr (TiO2:Ta/Cr) enhanced photocatalytic activity for O2 evolution by water oxidation under visible irradiation (>2.2 eV). The enhanced visible light activity of H2-treated TiO2:Ta/Cr was attributed to the increase of electron concentration, which was confirmed by UV-vis diffuse reflectance and electron spin resonance (ESR) spectroscopy. The H2-treated TiO2:Ta/Cr photocatalyst was repeatedly used in aqueous media in spite of the presence of doped electrons. Photoluminescence and transient absorption spectroscopies revealed that electron doping with H2 treatment decreased the midgap states working as deep traps of photoexcited electrons and increased the accumulation of the photoexcited electrons in the conduction band. The optimized H2 reduction temperature was decreased with an increase in the amount of higher valence Ta5+ used as a donor-type dopant. This study shows that the precise control of the bulk electronic structure of rutile TiO2 by a combination of codoping and H2 reduction treatment improves the visible-light-driven photocatalytic activity because of the decrease of the trapping sites at deep energy levels and the recombination between deeply trapped electrons and valence band holes.

Original languageEnglish
Pages (from-to)3274-3282
Number of pages9
JournalACS Applied Energy Materials
Volume2
Issue number5
DOIs
Publication statusPublished - May 28 2019
Externally publishedYes

Keywords

  • chromium
  • photoexcited electron dynamics
  • reduced rutile
  • tantalum
  • titanium dioxide
  • visible light
  • water oxidation

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrochemistry
  • Materials Chemistry
  • Electrical and Electronic Engineering

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