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A two-dimensional phase of TiO2 with a reduced bandgap

Nature Chemistry volume 3, pages 296–300 (2011)Cite this article

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Abstract

Titanium dioxide is the prototypical transition metal oxide photocatalyst. However, the larger than 3 eV bandgap of common bulk phases of TiO2 limits its light absorption to UV light, making it inefficient for solar energy conversion. Attempts at increasing visible light activity by narrowing the bandgap of TiO2 through doping have proven difficult, because of defect-induced charge trapping and recombination sites of photo-excited charge carriers. Here, we report the existence of a dopant-free, pure TiO2 phase with a narrow bandgap. This new pure TiO2 phase forms on the surface of rutile TiO2(011) by oxidation of bulk titanium interstitials. We measure a bandgap of only ~2.1 eV for this new phase, matching it closely with the energy of visible light.

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Figure 1: Atomic-resolution STM images of the rutile TiO2(011) surface.
Figure 2: Scanning tunnelling spectroscopy (STS) measurements.
Figure 3: Comparison of TiO2 phases by photoemission spectroscopy.
Figure 4: Resonant photoemission measurement for the valence band maximum of the new TiO2 phase.

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Acknowledgements

The photoemission data were collected at the Center for Advanced Microstructures and Devices (CAMD) in Baton Rouge, LA, operated by the Louisiana State University (LSU). The authors acknowledge financial support from the US Department of Energy, Office of Basic Energy Sciences (grant no. DE-SC0001508).

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Authors and Affiliations

  1. Department of Physics, University of South Florida, Tampa, 33620, Florida, USA

    Junguang Tao, Tim Luttrell & Matthias Batzill

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  1. Junguang Tao
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  2. Tim Luttrell
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  3. Matthias Batzill
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Contributions

J.T. performed the experiments, analysed the data and wrote the paper. T.L. assisted with the experiments. M.B. directed the research and wrote the paper. All authors read and approved the contents of this manuscript.

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Correspondence to Matthias Batzill.

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The authors declare no competing financial interests.

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Tao, J., Luttrell, T. & Batzill, M. A two-dimensional phase of TiO2 with a reduced bandgap. Nature Chem 3, 296–300 (2011). https://doi.org/10.1038/nchem.1006

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