Photocatalytic properties of TiO2: evidence of the key role of surface active sites in water oxidation
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Date
2015-08-21
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Americal Chemical Society
Abstract
Photocatalytic activity of oxide semiconductors is commonly considered in terms of the effect of the band gap on the light-induced performance. The present work considers a combined effect of several key performance-related properties (KPPs) on photocatalytic activity of TiO2 (rutile), including the chemical potential of electrons (Fermi level), the concentration of surface active sites, and charge transport, in addition to the band gap. The KPPs have been modified using defect engineering. This approach led to imposition of different defect disorders and the associated KPPs, which are defect-related. This work shows, for the first time, a competitive influence of different KPPs on photocatalytic activity that was tested using oxidation of methylene blue (MB). It is shown that the increase of oxygen activity in the TiO2 lattice from 10–12 Pa to 105 Pa results in (i) increase in the band gap from 2.42 to 2.91 eV (direct transitions) or 2.88 to 3 eV (indirect transitions), (ii) increase in the population of surface active sites, (iii) decrease of the Fermi level, and (iv) decrease of the charge transport. It is shown that the observed changes in the photocatalytic activity are determined by two dominant KPPs: the concentration of active surface sites and the Fermi level, while the band gap and charge transport have a minor effect on the photocatalytic performance. The effect of the defect-related properties on photoreactivity of TiO2 with water is considered in terms of a theoretical model offering molecular-level insight into the process. Copyright © 2017 American Chemical Society
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Keywords
Oxides, Electrons, Fermi level, Charged-particle transport, Methylene blue, Photocatalysis
Citation
Bak, T., Li, W., Nowotny, J., Atanacio, A. J., & Davis, J. (2015). Photocatalytic properties of TiO2: evidence of the key role of surface active sites in water oxidation. Journal of Physical Chemistry A, 119(36), 9465-9473. doi:10.1021/acs.jpca.5b05031