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Mixed water/OH structures on Pd(1 1 1)

Authors
Journal
Surface Science
0039-6028
Publisher
Elsevier
Publication Date
Volume
601
Issue
2
Identifiers
DOI: 10.1016/j.susc.2006.10.024
Keywords
  • Desorption
  • Surface Reaction
  • Palladium
  • Water
  • Oh

Abstract

Abstract Chemisorbed O and water react on Pd(1 1 1) at low temperatures to form a mixed OH/H 2O layer with a (√3 × √3) R30° registry. Reaction requires at least two water molecules to each O before the (2 × 2)O islands are consumed, the most stable OH/water structure being a (OH + H 2O) layer containing 0.67 ML of oxygen, formed by the reaction 3H 2O + O → 2(H 2O + OH). This structure is stabilised compared to pure water structures, decomposing at 190 K as OH recombines and water desorbs. The (√3 × √3) R30° − (OH + H 2O) phase cannot be formed by O/H reaction and is distinct from the (√3 × √3) R30° structure formed by O/H coadsorption below 200 K. Mixed OH/water structures do not react with coadsorbed H below 190 K on Pd(1 1 1), preventing this phase catalyzing the low temperature H 2/O 2 reaction which only occurs at higher temperatures.

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