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  4. Formation of an electron hole doped film in the alpha-Fe2O3 photoanode upon electrochemical oxidation
 
research article

Formation of an electron hole doped film in the alpha-Fe2O3 photoanode upon electrochemical oxidation

Gajda-Schrantz, Krisztina
•
Tymen, Simon
•
Boudoire, Florent
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2013
Physical Chemistry Chemical Physics

Solar hydrogen generation by water splitting in photoelectrochemical cells (PEC) is an appealing technology for a future hydrogen economy. Hematite is a prospective photoanode material in this respect because of its visible light conjugated band gap, its corrosion stability, its environmentally benign nature and its low cost. Its bulk and surface electronic structure has been under scrutiny for many decades and is considered critical for improvement of efficiency. In the present study, hematite films of nominally 500 nm thickness were obtained by dip-coating on fluorine doped tin oxide (FTO) glass slides and then anodised in 1 molar KOH at 500, 600, and 700 mV for 1, 10, 120 and 1440 minutes under dark conditions. X-ray photoelectron spectra recorded at the Fe 3p resonant absorption threshold show that the e(g) transition before the Fermi energy, which is well developed in the pristine hematite film, becomes depleted upon anodisation. The spectral weight of the e(g) peak decreases with the square-root of the anodisation time, pointing to a diffusion controlled process. The speed of this process increases with the anodisation potential, pointing to Arrhenius behaviour. Concomitantly, the weakly developed t(2g) peak intensity becomes enhanced in the same manner. This suggests that the surface of the photoanode contains Fe2+ species which become oxidized toward Fe3+ during anodisation. The kinetic behaviour derived from the experimental data suggests that the anodisation forms an electron hole doped film on and below the hematite surface.

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Type
research article
DOI
10.1039/c2cp42597a
Web of Science ID

WOS:000313565300014

Author(s)
Gajda-Schrantz, Krisztina
Tymen, Simon
Boudoire, Florent
Toth, Rita
Bora, Debajeet K.
Calvet, Wolfram
Graetzel, Michael  
Constable, Edwin C.
Braun, Artur
Date Issued

2013

Publisher

Royal Society of Chemistry

Published in
Physical Chemistry Chemical Physics
Volume

15

Issue

5

Start page

1443

End page

1451

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LPI  
Available on Infoscience
March 28, 2013
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/90988
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