Abstract

Light-driven plasmonic enhancement of chemical reactions on metal catalysts is a promising strategy to achieve highly selective and efficient chemical transformations. The study of plasmonic catalyst materials has traditionally focused on late transition metals such as Au{,} Ag{,} and Cu. In recent years{,} there has been increasing interest in the plasmonic properties of a set of earth-abundant elements such as Mg{,} which exhibit interesting hydrogenation chemistry with potential applications in hydrogen storage. This work explores the optical{,} electronic{,} and catalytic properties of a set of metallic Mg nanoclusters with up to 2057 atoms using time-dependent density functional tight-binding and density functional theory calculations. Our results show that Mg nanoclusters are able to produce highly energetic hot electrons with energies of up to 4 eV. By electronic structure analysis{,} we find that these hot electrons energetically align with electronic states of physisorbed molecular hydrogen{,} occupation of which by hot electrons can promote the hydrogen dissociation reaction. We also find that the reverse reaction{,} hydrogen evolution on metallic Mg{,} can potentially be promoted by hot electrons{,} but following a different mechanism. Thus{,} from a theoretical perspective{,} Mg nanoclusters display very promising behaviour for their use in light promoted storage and release of hydrogen.