Dynamics of photogenerated holes in surface modified α-Fe₂O₃ photoanodes for solar water splitting

This paper addresses the origin of the decrease in the external electrical bias required for water photoelectrolysis with hematite photoanodes, observed following surface treatments of such electrodes. We consider two alternative surface modifications: a cobalt oxo/hydroxo-based (CoO ₓ) overlayer, r...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2012-09, Vol.109 (39), p.15640-15645
Main Authors: Barroso, Monica, Mesa, Camilo A, Pendlebury, Stephanie R, Cowan, Alexander J, Hisatomi, Takashi, Sivula, Kevin, Grätzel, Michael, Klug, David R, Durrant, James R
Format: Article
Language:English
Subjects:
absorption
Absorption spectra
CHEMICAL APPROACHES TO ARTIFICIAL PHOTOSYNTHESIS: SOLAR FUELS SPECIAL FEATURE
cobalt
Electric current
Electrodes
Electrons
Ferric Compounds - chemistry
Hematite
iron
Material films
Materials
Oxidation
Oxidation-Reduction
Oxides
Photochemical Processes
Physical Sciences
Solar Energy
Water - chemistry
Water splitting
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Summary:This paper addresses the origin of the decrease in the external electrical bias required for water photoelectrolysis with hematite photoanodes, observed following surface treatments of such electrodes. We consider two alternative surface modifications: a cobalt oxo/hydroxo-based (CoO ₓ) overlayer, reported previously to function as an efficient water oxidation electrocatalyst, and a Ga ₂O ₃ overlayer, reported to passivate hematite surface states. Transient absorption studies of these composite electrodes under applied bias showed that the cathodic shift of the photocurrent onset observed after each of the surface modifications is accompanied by a similar cathodic shift of the appearance of long-lived hematite photoholes, due to a retardation of electron/hole recombination. The origin of the slower electron/hole recombination is assigned primarily to enhanced electron depletion in the Fe ₂O ₃ for a given applied bias.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1118326109