Reaction of SeF6 with iron and iron oxide surfaces: a model for selenate reduction

The reaction of SeF6 with Fe and Fe oxide surfaces is investigated as a model of the reduction of aqueous selenate. Polycrystalline iron foils were reacted with gaseous SeF6 in vacuum and then characterized by X-ray photoelectron spectroscopy. A novel use of electron stimulated desorption was used to determine if any SeF bonds remain following reaction. It was found that SeF6 completely dissociates, growing a film of FeF2. The growth initially follows Mott–Cabrera kinetics, but then abruptly stops. Thin Fe oxide layers on the surface impede the adsorption of SeF6. It is suggested that the fluoride and oxide films both quench the reaction by inhibiting the transport of electrons that are needed to dissociate SeF6 at the surface.