Properties of adsorbed oxygen on Au/SiO2

Oxygen adsorption on silica-supported gold catalyst from NO₂ and O₂ exposures were investigated by temperature-programmed desorption spectroscopy under a vacuum condition. NO₂ and O₂ exposures of the surface of the catalyst at room temperature gave adsorbed oxygen in atomic state. Adsorbed oxygen penetrated beneath the gold with lower activation energy for NO₂ exposure than for O₂ exposure. Adsorbed oxygen in oxidic state which was desorbed above 600 K altered the surface properties of gold and resulted in the decrease of activation energy for oxygen to penetrate beneath the gold surface.