Adsorption and dissociation of N2 on rhenium single crystal surfaces

G. Haase*, M. Asscher

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

40 Scopus citations

Abstract

The interaction of N2 with a rhenium polycrystalline foil, Re(0001) and Re(11-20) single crystal surfaces was studied under ultrahigh vacuum conditions at the temperature range of 80-1800 K. Extrinsic precursor adsorption kinetics at 80 K on the two crystals imply that the binding energy of the second layer nitrogen molecules is only sligthly affected by the substrate's structure. Molecular nitrogen was found to adsorb on a single physisorption site on Re(0001) but at least two different binding energies were identified on Re(11-20) and the polycrystalline foil. The sticking coefficient into the molecular adsorption sites is 0.90±0.05 on the two single crystal surfaces at 80 K. Dissociation of nitrogen occurs at all three surfaces the initial dissociative sticking probabilities (S0) measured at 218 K are (4±1)×10-4 and (9±2)×10-6 for the Re(11-20) and Re(0001), respectively. The polycrystalline foil was found to be most effective for the dissociation of nitrogen with a probability of 0.25 at low coverage which decreases to 0.025 at saturation coverage. Study of the dissociative sticking probability as a function of crystal temperature implies the existence of a barrier for dissociative chemisorption of 6±1 kJ/mol and 14±2 kJ/mol on the Re(11-20) and the Re(0001) single crystal surfaces, respectively. The reactivity for nitrogen dissociation of these surfaces is in agreement with high pressure ammonia synthesis study over the same surfaces.

Original languageEnglish
Pages (from-to)75-92
Number of pages18
JournalSurface Science
Volume191
Issue number1-2
DOIs
StatePublished - 1987

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