Mechanisms of Pd(1 1 0) surface reconstruction and oxidation: XPS, LEED and TDS study

• Published in: Surface science 2006-09, Vol.600 (18), p.4119-4125
• Main Authors: Titkov, A.I., Salanov, A.N., Koscheev, S.V., Boronin, A.I.
• Format: Article
• Language: English
• Subjects: Catalysis; Chemisorption; Oxidation; Palladium; Single crystal surfaces; Thermal desorption spectroscopy; X-ray photoelectron spectroscopy
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2006.01.131

Oxygen interaction with Pd(1 1 0) has been studied in a wide range of pressures (Po 2 = 10 −6–100 Pa) and temperatures ( T = 400–600 K) by X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and thermal desorption spectroscopy (TDS). The amount of oxygen absorbed by Pd(1 1 0) single crystal grows to more than 100 ML when the reaction temperature and the O 2 exposure are increased. Several reconstructed and oxide structures are sequentially formed on Pd(1 1 0) as the amount of adsorbed and absorbed oxygen increases. During oxygen adsorption (1 × 2) reconstruction occurs and a c(2 × 4) structure is formed on Pd(1 1 0) at θ = 0.5 ML. When the amount of absorbed oxygen increases from 0.5 to 2.0 ML, oxygen penetrates into subsurface Pd layers to the depth exceeding 15–20 Å while retaining the c(2 × 4) structure. When the amount of absorbed oxygen is between 2 and 5 ML, the surface is subjected to reconstruction with the formation of a surface oxide with θ ∼ 0.8 that has a complex LEED diffraction pattern. Further increase of the amount of absorbed oxygen beyond 5 ML leads to oxygen location in the subsurface region forming PdO clusters. They gradually grow to form an almost continuous layer composed of PdO clusters.