Alternative Mechanisms in Hydrogen Production by Aluminum Anion Clusters.

Possible mechanisms for the reaction of aluminum anion clusters with water have been studied theoretically using density functional theory for four different size clusters. Our results confirm the previously found (Reber et al. J. Phys. Chem. A2010, 114, 6071) importance of Lewis-acid and Lewis-base sites on the cluster in the size specificity of the reactivity. However, alternative viable mechanisms have been found using both Langmuir-Hinshelwood and Eley-Rideal kinetics. Grotthuss-like mechanisms appear to be the most energetically favorable. We show that while the superatom theory successfully predicts reactivity of smaller clusters, it is less useful for the larger clusters.