Molecular and dissociative adsorption of water at low-index V 2O 5 surfaces: DFT studies using cluster surface models

Abstract

The adsorption of water in both the molecular and dissociative manners at low-index (0 1 0), (1 0 0) and (0 0 1) surfaces of V 2O 5 is examined by DFT methods using an embedded cluster model approach. The calculations showed that on saturated basal net planes ((0 1 0)V 2O 5), water is stabilized only in molecular form as a result of weak electrostatic interactions, and it may migrate through the surface. At unsaturated side planes ((1 0 0) and (0 0 1) surfaces), both the molecular and dissociative adsorption of water is possible. Molecular stabilization takes place at V centres via coordinative covalent bonds. On the (0 0 1) surface, dissociative adsorption is associated with a moderate energy barrier near bridging oxygen centres and with a very low barrier close to bridging oxygen sites connected to V atoms from different “valley”-like atomic layers. On the (1 0 0) net plane, water undergoes dissociation near the singly and doubly coordinated oxygen sites, although the process is probable only close to the twofold coordinated centre because proximity to vanadyl oxygen sites is accompanied by a high energy barrier.