ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
In order to investigate microscopic steps of ammonia synthesis on Ru surfaces, hydrogen adsorption on a Ru(0001) surface, precovered by atomic nitrogen, has been studied using high-resolution electron energy loss spectroscopy (HREELS) and thermal desorption spectroscopy (TDS). Hydrogen adsorption has been performed with the Ru sample at 90 and 300 K. At 90 K, the saturation coverage of hydrogen decreases with increasing N precoverage. The vibrational properties of H do not change much in the presence of N compared to those on the bare Ru(0001) surface exhibiting one single mode at 85 meV for small H coverages and losses at 99 and 141 meV at H saturation. Heating of the H+N coadsorbed layer from 90 to 300 K does not result in any observable N–H bond formation. After exposure of N/Ru(0001) to H2 at room temperature, however, NH3 and NH species are observed on the surface. NH3 is characterized by its symmetric bending mode δs at 145 meV. The reaction intermediate NH is stable up to 400 K and shows losses of ν(Ru-NH), δ(N–H), and ν(N–H) at 86, 166, and 410 meV, respectively. A barrier height of 93 kJ/mol is estimated for the NH3 synthesis reaction from N and H. In the presence of some coadsorbed Cs, NHx species are not observed at 300 K indicating a destabilization of NHx by Cs. © 1995 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.468930
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