A theoretical study of the H O and H S chemisorption on 2 2 Cu O 111/

Density functional theory coupled to the molecular cluster approach has been used to study the bonding of two Brønsted acids H2X, XsO and S.to the Cu2O 111. non-polar surface. Both molecular and dissociative chemisorption have been considered. The interaction between surface Cu I. Lewis acid sites and the nucleophilic X end of the undissociated H2X has been investigated for different molecular orientations, i.e., with the molecular plane either perpendicular atopH.or parallel atop.to the surface. As far as the dissociative chemisorption is concerned, both partial and total deprotonation of H X 5 2 have been considered. For both acids, the atop chemisorption corresponds to the absolute minimum, even if the partial 5 deprotonation of H2S is found isoenergetic to H2S atop5 . q1999 Elsevier Science B.V. All rights reserved