Pathways between superoxide and peroxide species on small La-O clusters

Abstract

Density functional theory calculations were used to investigate the connection between superoxide and peroxide species on La-O clusters. In the singlet state, a superoxide species can transition into a peroxide species by moving through a substantial energy barrier via a series of ozonides. In the triplet state, there is no connection between the two species, although there are two paths (singlet and triplet) that allow the interaction and subsequent transformation of two superoxide molecules on a La-O cluster. The superoxide species readily transitions to a peroxide species through a triplet pathway (O 2 − + O 2 − ↔ O 2 2− + O 2 ), in which the superoxide species undergoes rapid exchange with the peroxide. In the singlet path, however, the superoxide species must move through a pronounced energy barrier to change into a peroxide species, demonstrating that these oxygen species are highly stable in the singlet state. Superoxide species over La-O clusters are in rapid exchange with peroxide species in the triplet channel while superoxide and peroxide species are both relatively stable in the singlet channel.