Ammonia decomposition on Ir(100): From ultrahigh vacuum to elevated pressures

T. V. Choudhary, A. K. Santra, C. Sivadinarayana, Byoung Koun Min, C. W. Yi, K. Davis, D. W. Goodman

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Ammonia decomposition on Ir(100) has been studied over the pressure range from ultrahigh vacuum to 1.5 Torr and at temperatures ranging from 200 to 800 K. The kinetics of the ammonia decomposition reaction was monitored by total pressure change. The apparent activation energy obtained in this study (84 kJ/mol) is in excellent agreement with our previous studies using supported Ir catalysts (Ir/Al 2O 3 82 kJ/mol). Partial pressure dependence studies of the reaction rate yielded a positive order (0.9 ± 0.1) with respect to ammonia and negative order (-0.7 ±0.1) with respect to hydrogen. Temperature-programmed desorption data from clean and hydrogen co-adsorbed Ir(100) surfaces indicate that ammonia undergoes facile decomposition on both these surfaces. Recomhinative desorption of N 2 is the rate-determining step with a desorption activation energy of ∼63 kJ/mol. Co-adsorption data also indicate that the observed negative order with respect to hydrogen pressure is due to enhancement of the reverse reaction (NH x + H → NH x+1,x = 0-2) in the presence of excess H atoms on the surface.

Original languageEnglish
Pages (from-to)1-5
Number of pages5
JournalCatalysis Letters
Volume77
Issue number1-3
DOIs
Publication statusPublished - 2001 Dec 1
Externally publishedYes

Fingerprint

Ultrahigh vacuum
Ammonia
ultrahigh vacuum
ammonia
Decomposition
decomposition
Hydrogen
desorption
Desorption
hydrogen
Activation energy
activation energy
Temperature programmed desorption
Catalyst supports
Partial pressure
pressure dependence
Reaction rates
partial pressure
reaction kinetics
Adsorption

Keywords

  • Ammonia
  • Co-adsorption
  • CO -free
  • Decomposition
  • Hydrogen production

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

Cite this

Choudhary, T. V., Santra, A. K., Sivadinarayana, C., Min, B. K., Yi, C. W., Davis, K., & Goodman, D. W. (2001). Ammonia decomposition on Ir(100): From ultrahigh vacuum to elevated pressures. Catalysis Letters, 77(1-3), 1-5. https://doi.org/10.1023/A:1012754319273

Ammonia decomposition on Ir(100) : From ultrahigh vacuum to elevated pressures. / Choudhary, T. V.; Santra, A. K.; Sivadinarayana, C.; Min, Byoung Koun; Yi, C. W.; Davis, K.; Goodman, D. W.

In: Catalysis Letters, Vol. 77, No. 1-3, 01.12.2001, p. 1-5.

Research output: Contribution to journalArticle

Choudhary, TV, Santra, AK, Sivadinarayana, C, Min, BK, Yi, CW, Davis, K & Goodman, DW 2001, 'Ammonia decomposition on Ir(100): From ultrahigh vacuum to elevated pressures', Catalysis Letters, vol. 77, no. 1-3, pp. 1-5. https://doi.org/10.1023/A:1012754319273
Choudhary TV, Santra AK, Sivadinarayana C, Min BK, Yi CW, Davis K et al. Ammonia decomposition on Ir(100): From ultrahigh vacuum to elevated pressures. Catalysis Letters. 2001 Dec 1;77(1-3):1-5. https://doi.org/10.1023/A:1012754319273
Choudhary, T. V. ; Santra, A. K. ; Sivadinarayana, C. ; Min, Byoung Koun ; Yi, C. W. ; Davis, K. ; Goodman, D. W. / Ammonia decomposition on Ir(100) : From ultrahigh vacuum to elevated pressures. In: Catalysis Letters. 2001 ; Vol. 77, No. 1-3. pp. 1-5.
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