Confinement of hydrogen and hydroxyl radicals in water cages: a density functional theory study

Abstract

Density functional theory calculations with D3 empirical dispersion correction reveal that hydrogen and hydroxyl radicals encapsulated in typical water cages found in clathrate hydrates exhibit similar structures and properties in their confined states to those in their corresponding free states, including atomic charges, spin densities, and electronic configurations. Diffusion studies reveal that energy barriers exist for these radicals to approach or exit these water cages. Energy decomposition analyses further reveal that coulombic repulsion between the radical and water cage is responsible for these energy barriers and the inability of these species to react with cage water molecules. This study provides insight into mechanisms for the storage of free radicals, which is normally extremely difficult because of their high reactivities toward many substances.