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Issue 1, 2008
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Tuning the optical and photoelectrochemical properties of surface-modified TiO2

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Surface-modification of TiO2 is found to be a powerful tool for manipulating the fundamental optical and photoelectrochemical properties of TiO2. High surface area nanocrystalline TiO2 was modified by urea pyrolysis products at different temperatures between 300 °C and 500 °C. Modification occurs through incorporation of nitrogen species containing carbon into the surface structure of titania. The N1s XPS binding energies are 399–400 eV and decrease with increasing modification temperature whereby the Ti2p3/2 peak is also shifted to lower binding energies by about 0.5 eV. With increasing modification temperature the optical bandgap of surface-modified TiO2 continuously decreases down to ∼2.1 eV and the quasi-Fermi level of electrons at pH 7 is gradually shifted from –0.6 V to –0.3 V vs.NHE. The surface-modified materials show enhanced sub-bandgap absorption (Urbach tail) and exhibit photocurrents in the visible down to 750 nm. The maximum incident photon-to-current efficiency (IPCE) was observed for the materials modified at 350 °C and 400 °C (IPCE ∼ 14% at 400 nm, and IPCE ∼ 1% at 550 nm, respectively). The efficiency of photocurrent generation is limited by surface recombination, which leads to a significant decrease in IPCE values and significantly changes the shape of the IPCE spectra in dependence on the optical bandgap.

Graphical abstract: Tuning the optical and photoelectrochemical properties of surface-modified TiO2

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The article was received on 30 Jul 2007, accepted on 29 Oct 2007 and first published on 12 Nov 2007

Article type: Paper
DOI: 10.1039/B711658F
Citation: Photochem. Photobiol. Sci., 2008,7, 40-48

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    Tuning the optical and photoelectrochemical properties of surface-modified TiO2

    R. Beranek and H. Kisch, Photochem. Photobiol. Sci., 2008, 7, 40
    DOI: 10.1039/B711658F

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