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Adsorption of organic molecules at the TiO2(110) surface: the effect of van der Waals interactions

Tillotson, M., Brett, P., Bennett, R. A. and Grau-Crespo, R. (2015) Adsorption of organic molecules at the TiO2(110) surface: the effect of van der Waals interactions. Surface Science, 632 (142). pp. 142-153. ISSN 0039-6028

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To link to this item DOI: 10.1016/j.susc.2014.09.017

Abstract/Summary

Understanding the interaction of organic molecules with TiO2 surfaces is important for a wide range of technological applications. While density functional theory (DFT) calculations can provide valuable insight about these interactions, traditional DFT approaches with local exchange-correlation functionals suffer from a poor description of non-bonding van der Waals (vdW) interactions. We examine here the contribution of vdW forces to the interaction of small organic molecules (methane, methanol, formic acid and glycine) with the TiO2 (110) surface, based on DFT calculations with the optB88-vdW functional. The adsorption geometries and energies at different configurations were also obtained in the standard generalized gradient approximation (GGA-PBE) for comparison. We find that the optB88-vdW consistently gives shorter surface adsorbate-to-surface distances and slightly stronger interactions than PBE for the weak (physisorbed) modes of adsorption. In the case of strongly adsorbed (chemisorbed) molecules both functionals give similar results for the adsorption geometries, and also similar values of the relative energies between different chemisorption modes for each molecule. In particular both functionals predict that dissociative adsorption is more favourable than molecular adsorption for methanol, formic acid and glycine, in general agreement with experiment. The dissociation energies obtained from both functionals are also very similar, indicating that vdW interactions do not affect the thermodynamics of surface deprotonation. However, the optB88-vdW always predicts stronger adsorption than PBE. The comparison of the methanol adsorption energies with values obtained from a Redhead analysis of temperature programmed desorption data suggests that optB88-vdW significantly overestimates the adsorption strength, although we warn about the uncertainties involved in such comparisons.

Item Type:Article
Refereed:Yes
Divisions:Interdisciplinary centres and themes > Chemical Analysis Facility (CAF)
Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:37730
Publisher:Elsevier

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