An XPS study of the adsorption of oxygen on silver and platinum surfaces covered with potassium or cesium

Abstract

Adsorption of oxygen has been investigated on silver and platinum surfaces covered with potassium or cesium by X-ray photoelectron spectroscopy. Three types of oxygen species, viz., molecularly chemisorbed, O^δ-₂, dissociatively chemisorbed, O^x- (δ, x < 2), and oxide (or sub-surface oxygen), O^2-, are seen on potassium covered silver surface. While at smaller cesium coverages, both dissociatively chemisorbed, O^x-, and the oxide oxygen, O^2-, have been observed on silver, the dissociatively chemisorbed, O^x-, and the molecularly chemisorbed oxygen, O^δ-₂, are seen at very high cesium coverages. The dissociated oxygen is the main species present on platinum covered with either potassium or cesium. Surface concentrations of oxygen on both metal surfaces have been estimated over a wide range of alkali coverages (1 × 10¹⁴ to 1.8 × 10¹⁵ atoms/cm²) and temperatures (300 to 800 K).