Oxygen interaction with Pd(110) was studied in a wide range of pressures (PO2 = 10−6 to 100Pa) and 400 to 600K by X-ray photo-electron spectroscopy, low-energy electron diffraction and thermal desorption spectroscopy. The amount of oxygen absorbed by Pd(110) single crystal grows to more than 100ML when the reaction temperature and the O2 exposure were increased. Several reconstructed and oxide structures were sequentially formed on Pd(110) as the amount of adsorbed and absorbed oxygen increases. During oxygen adsorption (1 x 2) reconstruction occurred and a c(2 x 4) structure was formed on Pd(110) at a coverage of 0.5ML. When the amount of absorbed oxygen increases from 0.5 to 2.0ML, oxygen penetrated into sub-surface Pd layers to the depth exceeding 15 to 20Å while retaining the c(2 x 4) structure. When the amount of absorbed oxygen was between 2 and 5ML, the surface was subjected to reconstruction with the formation of a surface oxide with a coverage of ≈0.8 that had a complex low-energy electron diffraction pattern. Further increase of the amount of absorbed oxygen beyond 5ML led to oxygen location in the sub-surface region forming PdO clusters. They gradually grow to form an almost continuous layer composed of PdO clusters.

Mechanisms of Pd(110) Surface Reconstruction and Oxidation - XPS, LEED and TDS Study. A.I.Titkov, A.N.Salanov, S.V.Koscheev, A.I.Boronin: Surface Science, 2006, 600[18], 4119-25