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Determination of photoelectrochemical water oxidation intermediates on haematite electrode surfaces using operando infrared spectroscopy

Nature Chemistry volume 8, pages 778–783 (2016)Cite this article

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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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Figure 1: Experimental set-up and results of infrared spectroscopy measurements during electrochemical and PEC water oxidation.
Figure 2: Plots of the measured current and infrared absorption spectra of haematite electrodes in response to illumination and an applied potential.
Figure 3: Plot of the effect of oxygen isotopic variation on the infrared absorption spectra during PEC water oxidation with haematite 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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  1. Omid Zandi

    Present address: Present address: McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712-1589, USA,

Authors and Affiliations

  1. Department of Chemistry, Michigan State University, 578 S Shaw Lane, East Lansing, 48824-1322, Michigan, USA

    Omid Zandi & Thomas W. Hamann

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Contributions

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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Correspondence to Thomas W. Hamann.

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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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