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Issue 43, 2012
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The effect of oxygen vacancies on the binding interactions of NH3 with rutile TiO2(110)-1 × 1

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Abstract

A series of NH3 temperature-programmed desorption (TPD) spectra were taken after dosing NH3 at 70 K on rutile TiO2(110)-1 × 1 surfaces with oxygen vacancy (VO) concentrations of ∼0% (p-TiO2) and 5% (r-TiO2), respectively, to study the effect of VOs on the desorption energy of NH3 as a function of coverage, θ. Our results show that in the zero coverage limit, the desorption energy of NH3 on r-TiO2 is 115 kJ mol−1, which is 10 kJ mol−1 less than that on p-TiO2. The desorption energy from the Ti4+ sites decreases with increasing θ due to repulsive NH3–NH3 interactions and approaches ∼55 kJ mol−1 upon the saturation of Ti4+ sites (θ = 1 monolayer, ML) on both p- and r-TiO2. The absolute monolayer saturation coverage is determined to be about 10% smaller on r-TiO2 than that on p-TiO2. Additionally, the trailing edges of the NH3 TPD spectra on the hydroxylated TiO2(110) (h-TiO2) appear to be the same as that on r-TiO2 while those on oxidized TiO2(110) (o-TiO2) shift to higher temperatures. We present a detailed analysis of the results and reconcile the observed differences based on the repulsive adsorbate–adsorbate dipole interactions between neighboring NH3 molecules and the surface charge associated with the presence of VOs.

Graphical abstract: The effect of oxygen vacancies on the binding interactions of NH3 with rutile TiO2(110)-1 × 1

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Publication details

The article was received on 07 Aug 2012, accepted on 13 Sep 2012 and first published on 14 Sep 2012


Article type: Paper
DOI: 10.1039/C2CP42754K
Citation: Phys. Chem. Chem. Phys., 2012,14, 15060-15065
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    The effect of oxygen vacancies on the binding interactions of NH3 with rutile TiO2(110)-1 × 1

    B. Kim, Z. Li, B. D. Kay, Z. Dohnálek and Y. K. Kim, Phys. Chem. Chem. Phys., 2012, 14, 15060
    DOI: 10.1039/C2CP42754K

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