New insights into water splitting at mesoporous alpha-Fe2O3 films: a study by modulated transmittance and impedance spectroscopies
journal contribution
posted on 2014-09-04, 14:20authored byCharles Y. Cummings, Frank Marken, Laurence M. Peter, Upul 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.
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/