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Issue 6, 2012
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Electrochemical and photoelectrochemical investigation of water oxidation with hematite electrodes

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Abstract

Atomic layer deposition (ALD) was utilized to deposit uniform thin films of hematite (α-Fe2O3) on transparent conductive substrates for photocatalytic water oxidation studies. Comparison of the oxidation of water to the oxidation of a fast redox shuttle allowed for new insight in determining the rate limiting processes of water oxidation at hematite electrodes. It was found that an additional overpotential is needed to initiate water oxidation compared to the fast redox shuttle. A combination of electrochemical impedance spectroscopy, photoelectrochemical and electrochemical measurements were employed to determine the cause of the additional overpotential. It was found that photogenerated holes initially oxidize the electrode surface under water oxidation conditions, which is attributed to the first step in water oxidation. A critical number of these surface intermediates need to be generated in order for the subsequent hole-transfer steps to proceed. At higher applied potentials, the behavior of the electrode is virtually identical while oxidizing either water or the fast redox shuttle; the slight discrepancy is attributed to a shift in potential associated with Fermi level pinning by the surface states in the absence of a redox shuttle. A water oxidation mechanism is proposed to interpret these results.

Graphical abstract: Electrochemical and photoelectrochemical investigation of water oxidation with hematite electrodes

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Publication details

The article was received on 17 Feb 2012, accepted on 11 Apr 2012 and first published on 24 Apr 2012


Article type: Paper
DOI: 10.1039/C2EE21414H
Citation: Energy Environ. Sci., 2012,5, 7626-7636
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    Electrochemical and photoelectrochemical investigation of water oxidation with hematite electrodes

    B. Klahr, S. Gimenez, F. Fabregat-Santiago, J. Bisquert and T. W. Hamann, Energy Environ. Sci., 2012, 5, 7626
    DOI: 10.1039/C2EE21414H

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