A Facile Surface Passivation of Hematite Photoanodes with TiO2 Overlayers for Efficient Solar Water Splitting

Research output: Contribution to journalArticleResearchpeer review

Authors

  • M.G. Ahmed
  • I.E. Kretschmer
  • T.A. Kandiel
  • A.Y. Ahmed
  • F.A. Rashwan
  • D.W. Bahnemann
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Details

Original languageEnglish
Pages (from-to)24053-24062
Number of pages10
JournalACS Applied Materials and Interfaces
Volume7
Issue number43
Publication statusPublished - 21 Oct 2015

Abstract

The surface modification of semiconductor photoelectrodes with passivation overlayers has recently attracted great attention as an effective strategy to improve the charge-separation and charge-transfer processes across semiconductor-liquid interfaces. It is usually carried out by employing the sophisticated atomic layer deposition technique, which relies on reactive and expensive metalorganic compounds and vacuum processing, both of which are significant obstacles toward large-scale applications. In this paper, a facile water-based solution method has been developed for the modification of nanostructured hematite photoanode with TiO 2 overlayers using a water-soluble titanium complex (i.e., titanium bis(ammonium lactate) dihydroxide, TALH). The thus-fabricated nanostructured hematite photoanodes have been characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Photoelectrochemical measurements indicated that a nanostructured hematite photoanodes modified with a TiO 2 overlayer exhibited a photocurrent response ca. 4.5 times higher (i.e., 1.2 mA cm -2 vs RHE) than that obtained on the bare hematite photoanode (i.e., 0.27 mA cm -2 vs RHE) measured under standard illumination conditions. Moreover, a cathodic shift of ca. 190 mV in the water oxidation onset potential was achieved. These results are discussed and explored on the basis of steady-state polarization, transient photocurrent response, open-circuit potential, intensity-modulated photocurrent spectroscopy, and impedance spectroscopy measurements. It is concluded that the TiO 2 overlayer passivates the surface states and suppresses the surface electron-hole recombination, thus increasing the generated photovoltage and the band bending. The present method for the hematite electrode modification with a TiO 2 overlayer is effective and simple and might find broad applications in the development of stable and high-performance photoelectrodes.

Keywords

    TiO, hydrogen production, nanostructured hematite photoanodes, passivation overlayers, photoelectrochemistry, water splitting

ASJC Scopus subject areas

Sustainable Development Goals

Cite this

A Facile Surface Passivation of Hematite Photoanodes with TiO2 Overlayers for Efficient Solar Water Splitting. / Ahmed, M.G.; Kretschmer, I.E.; Kandiel, T.A. et al.
In: ACS Applied Materials and Interfaces, Vol. 7, No. 43, 21.10.2015, p. 24053-24062.

Research output: Contribution to journalArticleResearchpeer review

Ahmed, MG, Kretschmer, IE, Kandiel, TA, Ahmed, AY, Rashwan, FA & Bahnemann, DW 2015, 'A Facile Surface Passivation of Hematite Photoanodes with TiO2 Overlayers for Efficient Solar Water Splitting', ACS Applied Materials and Interfaces, vol. 7, no. 43, pp. 24053-24062. https://doi.org/10.1021/acsami.5b07065
Ahmed, M. G., Kretschmer, I. E., Kandiel, T. A., Ahmed, A. Y., Rashwan, F. A., & Bahnemann, D. W. (2015). A Facile Surface Passivation of Hematite Photoanodes with TiO2 Overlayers for Efficient Solar Water Splitting. ACS Applied Materials and Interfaces, 7(43), 24053-24062. https://doi.org/10.1021/acsami.5b07065
Ahmed MG, Kretschmer IE, Kandiel TA, Ahmed AY, Rashwan FA, Bahnemann DW. A Facile Surface Passivation of Hematite Photoanodes with TiO2 Overlayers for Efficient Solar Water Splitting. ACS Applied Materials and Interfaces. 2015 Oct 21;7(43):24053-24062. doi: 10.1021/acsami.5b07065
Ahmed, M.G. ; Kretschmer, I.E. ; Kandiel, T.A. et al. / A Facile Surface Passivation of Hematite Photoanodes with TiO2 Overlayers for Efficient Solar Water Splitting. In: ACS Applied Materials and Interfaces. 2015 ; Vol. 7, No. 43. pp. 24053-24062.
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title = "A Facile Surface Passivation of Hematite Photoanodes with TiO2 Overlayers for Efficient Solar Water Splitting",
abstract = "The surface modification of semiconductor photoelectrodes with passivation overlayers has recently attracted great attention as an effective strategy to improve the charge-separation and charge-transfer processes across semiconductor-liquid interfaces. It is usually carried out by employing the sophisticated atomic layer deposition technique, which relies on reactive and expensive metalorganic compounds and vacuum processing, both of which are significant obstacles toward large-scale applications. In this paper, a facile water-based solution method has been developed for the modification of nanostructured hematite photoanode with TiO 2 overlayers using a water-soluble titanium complex (i.e., titanium bis(ammonium lactate) dihydroxide, TALH). The thus-fabricated nanostructured hematite photoanodes have been characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Photoelectrochemical measurements indicated that a nanostructured hematite photoanodes modified with a TiO 2 overlayer exhibited a photocurrent response ca. 4.5 times higher (i.e., 1.2 mA cm -2 vs RHE) than that obtained on the bare hematite photoanode (i.e., 0.27 mA cm -2 vs RHE) measured under standard illumination conditions. Moreover, a cathodic shift of ca. 190 mV in the water oxidation onset potential was achieved. These results are discussed and explored on the basis of steady-state polarization, transient photocurrent response, open-circuit potential, intensity-modulated photocurrent spectroscopy, and impedance spectroscopy measurements. It is concluded that the TiO 2 overlayer passivates the surface states and suppresses the surface electron-hole recombination, thus increasing the generated photovoltage and the band bending. The present method for the hematite electrode modification with a TiO 2 overlayer is effective and simple and might find broad applications in the development of stable and high-performance photoelectrodes. ",
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T1 - A Facile Surface Passivation of Hematite Photoanodes with TiO2 Overlayers for Efficient Solar Water Splitting

AU - Ahmed, M.G.

AU - Kretschmer, I.E.

AU - Kandiel, T.A.

AU - Ahmed, A.Y.

AU - Rashwan, F.A.

AU - Bahnemann, D.W.

N1 - Publisher Copyright: © 2015 American Chemical Society. Copyright: Copyright 2015 Elsevier B.V., All rights reserved.

PY - 2015/10/21

Y1 - 2015/10/21

N2 - The surface modification of semiconductor photoelectrodes with passivation overlayers has recently attracted great attention as an effective strategy to improve the charge-separation and charge-transfer processes across semiconductor-liquid interfaces. It is usually carried out by employing the sophisticated atomic layer deposition technique, which relies on reactive and expensive metalorganic compounds and vacuum processing, both of which are significant obstacles toward large-scale applications. In this paper, a facile water-based solution method has been developed for the modification of nanostructured hematite photoanode with TiO 2 overlayers using a water-soluble titanium complex (i.e., titanium bis(ammonium lactate) dihydroxide, TALH). The thus-fabricated nanostructured hematite photoanodes have been characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Photoelectrochemical measurements indicated that a nanostructured hematite photoanodes modified with a TiO 2 overlayer exhibited a photocurrent response ca. 4.5 times higher (i.e., 1.2 mA cm -2 vs RHE) than that obtained on the bare hematite photoanode (i.e., 0.27 mA cm -2 vs RHE) measured under standard illumination conditions. Moreover, a cathodic shift of ca. 190 mV in the water oxidation onset potential was achieved. These results are discussed and explored on the basis of steady-state polarization, transient photocurrent response, open-circuit potential, intensity-modulated photocurrent spectroscopy, and impedance spectroscopy measurements. It is concluded that the TiO 2 overlayer passivates the surface states and suppresses the surface electron-hole recombination, thus increasing the generated photovoltage and the band bending. The present method for the hematite electrode modification with a TiO 2 overlayer is effective and simple and might find broad applications in the development of stable and high-performance photoelectrodes.

AB - The surface modification of semiconductor photoelectrodes with passivation overlayers has recently attracted great attention as an effective strategy to improve the charge-separation and charge-transfer processes across semiconductor-liquid interfaces. It is usually carried out by employing the sophisticated atomic layer deposition technique, which relies on reactive and expensive metalorganic compounds and vacuum processing, both of which are significant obstacles toward large-scale applications. In this paper, a facile water-based solution method has been developed for the modification of nanostructured hematite photoanode with TiO 2 overlayers using a water-soluble titanium complex (i.e., titanium bis(ammonium lactate) dihydroxide, TALH). The thus-fabricated nanostructured hematite photoanodes have been characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Photoelectrochemical measurements indicated that a nanostructured hematite photoanodes modified with a TiO 2 overlayer exhibited a photocurrent response ca. 4.5 times higher (i.e., 1.2 mA cm -2 vs RHE) than that obtained on the bare hematite photoanode (i.e., 0.27 mA cm -2 vs RHE) measured under standard illumination conditions. Moreover, a cathodic shift of ca. 190 mV in the water oxidation onset potential was achieved. These results are discussed and explored on the basis of steady-state polarization, transient photocurrent response, open-circuit potential, intensity-modulated photocurrent spectroscopy, and impedance spectroscopy measurements. It is concluded that the TiO 2 overlayer passivates the surface states and suppresses the surface electron-hole recombination, thus increasing the generated photovoltage and the band bending. The present method for the hematite electrode modification with a TiO 2 overlayer is effective and simple and might find broad applications in the development of stable and high-performance photoelectrodes.

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KW - nanostructured hematite photoanodes

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KW - photoelectrochemistry

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