The influence of the local structure of Fe(III) on the photocatalytic activity of doped TiO2 photocatalysts-An EXAFS, XPS and Mossbauer spectroscopic study

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Abstract

Fe(III)-doped TiO2 based heterogeneous photocatalysts were prepared by the sol-gel technique (S samples) or flame hydrolysis (F samples). In photocatalytic phenol decomposition, the undoped F-sample performed much better, than the undoped S one. However, for the S samples, photocatalytic activity first increased with the increasing Fe(III) concentration, and then passed through a maximum, while Fe(III)-doping in F samples significantly decreased it, even at the smallest dopant level. Since the same dopant caused opposite photocatalytic effects in the two series, their structure was systematically compared to identify the underlying chemical and/or physical reasons. The photocatalysts were first characterized by AAS, DRS, XRD and TEM methods and it has been shown that the differences in the photocatalytic activity cannot be explained by the minor variations in the bulk structural properties of TiO2. Mossbauer and XP spectroscopic measurements performed on representative samples qualitatively proved that the local structure of Fe(III) is different in the two series. To quantify these effects, Fe-K edge X-ray absorption measurements were performed. From the pre-edge and XANES region it was learnt that Fe(III) was present in a distorted octahedral environment in both series, however, the extent of distortion is much more significant within the S than within the F one. Information obtained from the EXAFS region indicated that the structure of Fe2O3 was much more ordered in the F-series then in the S one and vacancies were more abundant in the S than in the F series. Moreover, the geometry around Fe(III) systematically varied within the S-series, which could explain, why photocatalytic activity passed through a maximum with the increasing Fe(III) concentration in these samples. (C) 2011 Elsevier B.V. All rights reserved.

Details

Authors
  • Eva G. Bajnoczi
  • Nandor Balazs
  • Karoly Mogyorosi
  • David F. Sranko
  • Zsolt Pap
  • Zoltan Ambrus
  • Sophie Canton
  • Katarina Norén
  • Erno Kuzmann
  • Attila Vertes
  • Zoltan Homonnay
  • Albert Oszko
  • Istvan Palinko
  • Pal Sipos
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Atom and Molecular Physics and Optics

Keywords

  • TiO2, Fe(III) doping, EXAFS, XPS, Mossbauer, Local structure, Photocatalysis
Original languageEnglish
Pages (from-to)232-239
JournalApplied Catalysis B: Environmental
Volume103
Issue number1-2
Publication statusPublished - 2011
Publication categoryResearch
Peer-reviewedYes

Bibliographic note

The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Chemical Physics (S) (011001060), Max-laboratory (011012005)