Adsorption of H2O on the (001) plane of V2O5: chemisorption site identification

The interaction of water molecules with a polycrystalline V2O5 surface has been investigated both by means of a semi-empirical quantum chemistry compu tational method and by temperature-programmed desorption (TPD). From the TP D desorption spectra, it was found that water desorbed from the V2O5 surfac e at a temperature T(p)approximate to 350 K with a heating rate of beta = 1 0 K min(-1). Peak temperature was coverage independent. We explored differe nt chemisorption sites of water molecules on the (001) plane of V2O5. Activ ation energies for each of these sites are calculated and compared with the thermal desorption spectra. From such a comparison we conclude that at roo m temperature, the water molecule bridges, by hydrogen bonding, two neighbo ring vanadyl oxygens O(1) with its plane preferentially parallel to the (00 1) substrate plane. The oxygen atom of the water molecule is above a vanadi um atom. TPD spectra are modeled by first order desorption kinetics with a desorption process activation energy of 23.8 kcal mol(-1), in agreement wit h the theoretical calculation of 22-23 kcal mol(-1). (C) 2000 Elsevier Scie nce B.V. All rights reserved.