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

Bajnoczi, Eva G.; Balazs, Nandor; Mogyorosi, Karoly; Sranko, David F.; Pap, Zsolt; Ambrus, Zoltan; Canton, Sophie LU ; Norén, Katarina LU ; Kuzmann, Erno and Vertes, Attila, et al. (2011) In Applied Catalysis B: Environmental 103(1-2). p.232-239
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... (More)
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. (Less)
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keywords
TiO2, Fe(III) doping, EXAFS, XPS, Mossbauer, Local structure, Photocatalysis
in
Applied Catalysis B: Environmental
volume
103
issue
1-2
pages
232 - 239
publisher
Elsevier
external identifiers
  • wos:000288884500029
  • scopus:79951942564
ISSN
0926-3373
DOI
10.1016/j.apcatb.2011.01.033
language
English
LU publication?
yes
id
1c1f5f81-e679-42e0-9bc3-87ab781eddf5 (old id 1925591)
date added to LUP
2011-05-11 13:25:25
date last changed
2017-10-08 03:56:47
@article{1c1f5f81-e679-42e0-9bc3-87ab781eddf5,
  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.},
  author       = {Bajnoczi, Eva G. and Balazs, Nandor and Mogyorosi, Karoly and Sranko, David F. and Pap, Zsolt and Ambrus, Zoltan and Canton, Sophie and Norén, Katarina and Kuzmann, Erno and Vertes, Attila and Homonnay, Zoltan and Oszko, Albert and Palinko, Istvan and Sipos, Pal},
  issn         = {0926-3373},
  keyword      = {TiO2,Fe(III) doping,EXAFS,XPS,Mossbauer,Local structure,Photocatalysis},
  language     = {eng},
  number       = {1-2},
  pages        = {232--239},
  publisher    = {Elsevier},
  series       = {Applied Catalysis B: Environmental},
  title        = {The influence of the local structure of Fe(III) on the photocatalytic activity of doped TiO2 photocatalysts-An EXAFS, XPS and Mossbauer spectroscopic study},
  url          = {http://dx.doi.org/10.1016/j.apcatb.2011.01.033},
  volume       = {103},
  year         = {2011},
}