Adsorption of metanol on titanium oxide investigated by DFT

V. M. SÁNCHEZ; E. DE LA LLAVE; D. A. SCHERLIS PEREL

Ciudad de Buenos Aires, Argentina

Workshop; Eighth Giambiagi Winter School (Part A) - Clusters, Molecules, Biomolecules and Materials; 2006

Titanium oxide surfaces play a central role in heterogeneous catalysis, given its ability to oxidize or deactivate organic substrates. In this work, we study the methanol adsorption on titanium dioxide clean surfaces using density functional theory (DFT). We focus our attention on anatase (101) and rutile (110), thermodynamically the most stable surfaces of TiO2. The geometrical and energetic parameters involved in the interaction between methanol and the surface in vacuum are characterized as a function of the adsorption mode (e. g. molecular or dissociated) and the degree of coverage. Most applications of titanium oxide, however, involve catalysis at a solid-liquid interface. The environment might affect the balance between the molecular and dissociated forms, or even inhibit the adsorption completely. In our calculations we specially take into account the solvent effect through a continuum model, which has been recently implemented within a DFT/Car-Parrinello molecular dynamics scheme. In this context the solvent is represented as a dielectric medium interacting self-consistently with the electronic charge of the adsorbate and the slab. With this approach we have investigated the different thermodynamics of the adsorption in a solution and in the gas phase.