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 language | English |
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Pages (from-to) | 75-92 |
Number of pages | 18 |
Journal | Surface Science |
Volume | 191 |
Issue number | 1-2 |
DOIs | |
State | Published - 1987 |