DFT studies of the adsorption and dissociation of H2O on the Al13 cluster: origins of this reactivity and the mechanism for H2 release.

ABSTRACT

A theoretical study of the chemisorption and dissociation pathways of water on the Al13 cluster was performed using the hybrid density functional B3LYP method with the 6-311+G(d, p) basis set. The activation energies, reaction enthalpies, and Gibbs free energy of activation for the reaction were determined. Calculations revealed that the H2O molecule is easily adsorbed onto the Al13 surface, forming adlayers. The dissociation of the first H2O molecule from the bimolecular H2O structure via the Grotthuss mechanism is the most kinetically favorable among the five potential pathways for O-H bond breaking. The elimination of H2 in the reaction of an H2O molecule with a hydrogen atom on the Al cluster via the Eley-Rideal mechanism has a lower activation barrier than the elimination of H2 in the reaction of two adsorbed H atoms or the reaction of OH and H. Following the adsorption and dissociation of H2O, the structure of Al13 is distorted to varying degrees.