UC Santa Barbara

We use density functional theory to examine methane dissociative adsorption on lanthana to produce H and CH3 bonded to the surface. Previous work suggested that the binding energy of a Lewis base and a Lewis acid to an oxide exceeds by far the value expected from adding the binding energies of the same compounds chemisorbed alone. This rule suggests that the fragments (H and CH3) formed by the dissociative adsorption of methane on an oxide will adsorb so that they could benefit from this strong acid-base interaction. To do this, one fragment must bind to oxygen and the other to a cation. Such a configuration should have lower energy than the one obtained by binding both fragments to oxygen, even though each fragment prefers to bind to oxygen when it binds alone. We suggest that this behavior is encountered in most systems. (Chemical Equation Presented).