Quantitative Structure of an Acetate Dye Molecule Analogue at the TiO2-Acetic Acid Interface
Hadeel Hussain1, Xavier Torrelles2, Gregory Cabailh3
1London Centre for Nanotechnology and Department of Chemistry, University College London, 20 Gordon Street, London WC1H OAJ, U.K.; ESRF, The European Synchrotron. 71, Avenue des Martyrs, CS40220, F-38043 Grenoble cedex 09, France.
Abstract:
The positions of atoms in and around acetate molecules at the rutile TiO2(110) interface with 0.1 M acetic acid have been determined with a precision of ±0.05 Å. Acetate is used as a surrogate for the carboxylate groups typically employed to anchor monocarboxylate dye molecules to TiO2 in dye-sensitized solar cells (DSSC). Structural analysis reveals small domains of ordered (2 × 1) acetate molecules, with substrate atoms closer to their bulk terminated positions compared to the clean UHV surface. Acetate is found in a bidentate bridge position, binding through both oxygen atoms to two 5-fold titanium atoms such that the molecular plane is along the [001] azimuth. Density functional theory calculations provide adsorption geometries in excellent agreement with experiment. The availability of these structural data will improve the accuracy of charge transport models for DSSC.
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