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Detailed study of the plasma-activated catalytic generation of ammonia in N2-H2 plasmas

Authors :
van Jh Jean-Pierre Helden
Jürgen Röpcke
Rab Rens Zijlmans
Rah Richard Engeln
G Göksel Yagci
Guillaume Lombardi
G.-D. Stancu
W Wiebe Wagemans
DC Daan Schram
Plasma & Materials Processing
Physics of Nanostructures
Plasma-based gas conversion
Source :
Journal of Applied Physics, 101(4):043305, 043305-1/12. American Institute of Physics
Publication Year :
2007

Abstract

We investigated the efficiency and formation mechanism of ammonia generation in recombining plasmas generated from mixtures of N2 and H2 under various plasma conditions. In contrast to the Haber-Bosch process, in which the molecules are dissociated on a catalytic surface, under these plasma conditions the precursor molecules, N2 and H2, are already dissociated in the gas phase. Surfaces are thus exposed to large fluxes of atomic N and H radicals. The ammonia production turns out to be strongly dependent on the fluxes of atomic N and H radicals to the surface. By optimizing the atomic N and H fluxes to the surface using an atomic nitrogen and hydrogen source ammonia can be formed efficiently, i.e., more than 10% of the total background pressure is measured to be ammonia. The results obtained show a strong similarity with results reported in literature, which were explained by the production of ammonia at the surface by stepwise addition reactions between adsorbed nitrogen and hydrogen containing radicals at the surface and incoming N and H containing radicals. Furthermore, our results indicate that the ammonia production is independent of wall material. The high fluxes of N and H radicals in our experiments result in a passivated surface, and the actual chemistry, leading to the formation of ammonia, takes place in an additional layer on top of this passivated surface.

Details

Language :
English
ISSN :
00218979
Volume :
101
Issue :
4
Database :
OpenAIRE
Journal :
Journal of Applied Physics
Accession number :
edsair.doi.dedup.....b3a43ec793a4a2f1a1c6f2af69e84d4b
Full Text :
https://doi.org/10.1063/1.2645828