Abstract
Water molecules were found to interact strongly with N2 when coadsorbed on Ru(001). This system was studied by TPD and work function change measurements. It was found that water molecules repel preadsorbed nitrogen at low water coverages (H20/Ru < 0.3). This is indicated by a shift of the thermal desorption peak to lower temperatures and by displacement of 20% of the saturation nitrogen coverage. At higher water coverages, a unique new N2 desorption peak gradually emerges and shifts from 105 to 167 K as water coverage increases to 9 bilayers. The extremely narrow molecular nitrogen TPD peak is indicative of the formation of a cage of hydrogen bonded water on top of trapped N2 molecules. Work function change measurements taken during adsorption and subsequently during sample heating in a Δφ-TPD mode suggest that the caged nitrogen molecules remain practically unperturbed inside the cage. Site-exchange model between nitrogen molecules escaping from the cage and water molecules which takes place upon sample heating, qualitatively explains the Δφ-TPD spectra. Deviations of the calculated curves based on this model from the observed data suggest structural rearrangements of the cage during the heating process.
Original language | English |
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Pages (from-to) | 250-258 |
Number of pages | 9 |
Journal | Surface Science |
Volume | 351 |
Issue number | 1-3 |
DOIs | |
State | Published - 1 May 1996 |
Keywords
- Nitrogen
- Ruthenium
- Solid-liquid interfaces
- Thermal desorption
- Water
- Work function measurements