An XPS study of molecularly chemisorbed oxygen on Ag(111)

An adsorbed oxygen species on Ag(111) which desorbs as O2 at ∽ 217 K has been examined by X-ray photoelectron spectroscopy. Its O(1s) spectrum differs significantly from the “peroxolike” O2-2,a species of Ag(110), which also desorbs near 200 K. The differences suggest that this species is more “superoxo-like” (O-2,a) in nature. Implications of this result for the mechanism of catalytic ethylene oxidation over Ag are discussed.