1. NH3 adsorption and decomposition on Ir(110): A combined temperature programmed desorption and high resolution fast x-ray photoelectron spectroscopy study.
- Author
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Weststrate, C. J., Bakker, J. W., Rienks, E. D. L., Lizzit, S., Petaccia, L., Baraldi, A., Vinod, C. P., and Nieuwenhuys, B. E.
- Subjects
SPECTRUM analysis ,SURFACE chemistry ,PHOTOELECTRON spectroscopy ,MOLECULAR spectroscopy ,CHEMICAL kinetics ,HYDROGENATION - Abstract
The adsorption and decomposition of NH
3 on Ir(110) has been studied in the temperature range from 80 K to 700 K. By using high-energy resolution x-ray photoelectron spectroscopy it is possible to distinguish chemically different surface species. At low temperature a NH3 multilayer, which desorbs at ∼110 K, was observed. The second layer of NH3 molecules desorbs around 140 K, in a separate desorption peak. Chemisorbed NH3 desorbs in steps from the surface and several desorption peaks are observed between 200 and 400 K. A part of the NH3ad decomposes into NHad between 225 and 300 K. NHad decomposes into Nad between 400 K and 500 K and the hydrogen released in this process immediately desorbs. N2 desorption takes place between 500 and 700 K via Nad combination. The steady state decomposition reaction of NH3 starts at 500 K. The maximum reaction rate is observed between 540 K and 610 K. A model is presented to explain the occurrence of a maximum in the reaction rate. Hydrogenation of Nad below 400 K results in NHad . No NH2ad or NH3ad /NH3 were observed. The hydrogenation of NHad only takes place above 400 K. On the basis of the experimental findings an energy scheme is presented to account for the observations. [ABSTRACT FROM AUTHOR]- Published
- 2005
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