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New insights into water splitting at mesoporous alpha-Fe2O3 films: a study by modulated transmittance and impedance spectroscopies

journal contribution
posted on 04.09.2014, 14:20 by Charles Y. Cummings, Frank Marken, Laurence M. Peter, Upul Wijayantha-Kahagala-GamageUpul Wijayantha-Kahagala-Gamage, Asif A. Tahir
Thin mesoporous films of α-Fe2O3 have been prepared on conducting glass substrates using layer-by-layer self-assembly of ca. 4 nm hydrous oxide nanoparticles followed by calcining. The electrodes were used to study the oxygen evolution reaction (OER) in the dark and under illumination using in situ potential-modulated absorption spectroscopy (PMAS) and light-modulated absorption spectroscopy (LMAS) combined with impedance spectroscopy. Formation of surface-bound higher-valent iron species (or “surface trapped holes”) was deduced from the PMAS spectra measured in the OER onset region. Similar LMAS spectra were obtained at more negative potentials in the onset region of photoelectrochemical OER, indicating involvement of the same intermediates. The impedance response of the mesoporous α-Fe2O3 electrodes exhibits characteristic transmission line behavior that is attributed to slow hopping of holes, probably between surface iron species. Frequency-resolved PMAS and LMAS measurements revealed slow relaxation behavior that can be related to the impedance response and that indicates that the lifetime of the intermediates (or trapped holes) involved in the OER is remarkably long.

Funding

K.G.U.W. and A.A.T. would like to acknowledge the support given by UK EPSRC

History

School

  • Science

Department

  • Chemistry

Published in

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY

Volume

134

Issue

2

Pages

1228 - 1234 (7)

Citation

CUMMINGS, C.Y. ... et al., 2012. New insights into water splitting at mesoporous alpha-Fe2O3 films: a study by modulated transmittance and impedance spectroscopies. Journal of the American Chemical Society, 134 (2), pp. 1228 - 1234.

Publisher

© American Chemical Society

Version

VoR (Version of Record)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Publication date

2012

Notes

Closed access. This article was published in the Journal of the American Chemical Society [© American Chemical Society] and the definitive version is available at: http://dx.doi.org/10.1021/ja209530s

ISSN

0002-7863

Language

en

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