CO dissociation on Ni: The effect of steps and of nickel carbonyl

Jakob Engbæk, Ole Lytken, Jane Hvolbæk Nielsen, Ib Chorkendorff

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The dissociation of CO was investigated on a stepped Ni(141313) crystal. The experiments show that the monoatomic steps completely dominate the dissociation of CO on the nickel surface. The activation energy for dissociation of CO along the steps is measured at 500 K to be 150 kJ/mol in the pressure range 1-7 X 10(-6) mbar CO. Poisoning the steps by preadsorbing 0.05 ML sulfur, the dissociation rate was reduced by more than a factor of 50 clearly providing evidence for the step activity. Furthermore, by deliberately adding remote amounts of nickel carbonyl (0.25%) to the CO gas, it is shown that the dissociation probability of CO is increased by a factor of 60 compared to when using a purified CO gas. This clearly demonstrates the importance of avoiding nickel carbonyl when CO dissociation is studied. CO dissociation is important because it is believed to be the rate limiting step in methanation and in the Fischer-Tropsch synthesis.
Original languageEnglish
JournalSurface Science
Volume602
Issue number3
Pages (from-to)733-743
ISSN0039-6028
DOIs
Publication statusPublished - 2008

Keywords

  • carbon monoxide
  • Fischer-Tropsch
  • methanation
  • nickel
  • surface defects
  • sulfur
  • nickel carbonyl
  • CO dissociation

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