INTERACTION OF ATOMIC OXYGEN WITH A POLYCRYSTALLINE Au SURFACE: XPS AND TPD STUDY

Adsorption of atomic oxygen on the surface of polycrystalline gold is studied in detail by XPS and TPD methods. It is shown that the action of atomic oxygen at initial stages leads to the formation of chemisorbed atomic oxygen with the deposition thickness T = 0-0.5 monolayers. Increased exposure to atomic oxygen leads to the formation of 2D gold oxide. At the maximum oxygen saturation, the calculated oxide layer thickness is 3 A, and its stoichiometry is close to AuO2. The TPD analysis shows that thermal stability of adsorbed oxygen is 510 K for the chemisorbed layer and 525 K for the 2D gold oxide. The structure of the 2D gold oxide is determined as one layer of gold atoms and two layers of oxygen atoms adsorbed on the surface and inside the subsurface layer. The reactivity of adsorbed oxygen is tested by the interaction of CO and H2 at room temperature; all the oxygen forms are shown to be active. It is established that the reactivity towards CO is 2 orders of magnitude higher than towards H-2, suggesting that oxygen species take part in the PROX mechanism.