A theoretical analysis of adsorption and dissociation of CH3OH on the stoichiometric SnO2(110) surface

A theoretical analysis based on the Hartree-Fock pseutdopotential method an d a density-functional theory calculation using a hybrid combination of gen eral gradient approximation with pseudopotential procedure has been carried out to study the adsorption and dissociation of methanol on the stoichiome tric SnO2(110) surface. The dependence of the results upon model system and computing method is discussed. An optimization procedure of adsorbate and substrate atom positions on a six-layer slab model has been selected to cha racterize the corresponding geometric parameters, adsorption energy and cha rge-transfer processes related with the molecularly adsorbed CH3OH and diss ociative channels to yield methoxy or methyl fragments. In the high-coverag e limit (theta = 1), we find that dissociation of the methanol molecule via the heterolylic cleavage of the C-O bond is favoured. At lower coverage (t heta = 1/2), this channel and the molecularly adsorbed methanol present sim ilar adsorption energies. (C) 1999 Elsevier Science B.V. All rights reserve d.