Abstract
Semiconductor electrodes capable of using solar photons to drive water-splitting reactions, such as haematite (α-Fe2O3), have been the subject of tremendous interest over recent decades. The surface has been found to play a significant role in determining the efficiency of water oxidation with haematite; however, previous works have only allowed hypotheses to be formulated regarding the identity of relevant surface species. Here we investigate the water-oxidation reaction on haematite using infrared spectroscopy under photoelectrochemical (PEC) water-oxidation conditions. A potential- and light-dependent absorption peak at 898 cm−1 is assigned to a FeIV=O group, which is an intermediate in the PEC water-oxidation reaction. These results provide direct evidence of high-valent iron–oxo intermediates as the product of the first hole-transfer reaction on the haematite surface and represent an important step in establishing the mechanism of PEC water oxidation on semiconductor electrodes.
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Acknowledgements
This work was supported by the National Science Foundation (CHE-1150378). The authors thank M. Bruening for the generous access to his infrared spectrometer.
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O.Z. and T.W.H. conceived and designed the experiments. O.Z. performed the experiments and analysed the data. O.Z. and T.W.H. co-wrote the paper.
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Zandi, O., Hamann, T. Determination of photoelectrochemical water oxidation intermediates on haematite electrode surfaces using operando infrared spectroscopy. Nature Chem 8, 778–783 (2016). https://doi.org/10.1038/nchem.2557
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DOI: https://doi.org/10.1038/nchem.2557
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