Metal-oxide Film Conversions Involving Large Anions

Abstract

Silver is a potential material for trapping fission product radioiodines and has the potential to safely transport and release radioiodines used in biomedical applications. However, reaction of I- with Ag could be complicated by the presence of silver oxide films. The kinetics of the conversion of Ag2O on Ag substrates to AgX (X = I or Br) are being followed by exposing electrochemically oxidized surfaces, with a known amount of Ag2O, to solutions containing I- or Br-. Results show that two conversion pathways are possible; (i) a direct chemical process; and (ii) a galvanically coupled process in which the cathodic reduction of Ag2O is coupled to the anodic oxidation of Ag to AgX. Scanning electron microscopy results also revealed a difference in crystal structure of AgX depending on the conversion pathway, with fine particles resulting from the chemical conversion, and larger, better defined crystals growing via galvanic coupling.