Low temperature adsorption of CO and 02 on Ni(100) and Ni(111): Evidence for precursors

Mansour Shayegan, Robert L. Park

Research output: Contribution to journalArticle

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Abstract

Studies of the adsorption of 02 and CO on different faces of single crystal Ni held at T~6 K are reported which provide direct evidence for a precursor adsorption preceding chemisorption. Values of the work function were obtained using the field-emission retarding potential method as Ni surfaces held at 6 K were exposed to 02 and CO and, subsequently, as the gas covered surfaces were annealed. Comparison with results for chemisorbed surfaces formed by gas exposure at 77 K indicates stabilized precursor adsorption phases at 6 K for O/Ni(111), O/Ni(100), and CO/ Ni(111). Starting at temperatures on the order of 20 K, these convert at appreciable rates to the usual chemisorption phases. Analysis of the temperature and time dependence of the reaction rates indicates activation energies EAof approximately 13, 6, and 4 meV for O/Ni(111), O/ Ni(100), and CO/Ni(lll), respectively. Precursor adsorption was not observed for CO/ Ni (100). Presumably the activation energy, if it exists, is too small for effective stabilization at 6 K.

Original languageEnglish (US)
Pages (from-to)1333-1335
Number of pages3
JournalJournal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
Volume4
Issue number3
DOIs
StatePublished - Jan 1 1986

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films

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