AVS 46th International Symposium
    Surface Science Division Monday Sessions
       Session SS2-MoA

Paper SS2-MoA6
Non-linear Behaviour in the NO-H@sub 2@ Reaction over Pt Group Metals: A Comparison

Monday, October 25, 1999, 3:40 pm, Room 607

Session: Reactions on Metals
Presenter: C.A. de Wolf, Leiden University, The Netherlands
Authors: C.A. de Wolf, Leiden University, The Netherlands
M.Yu. Smirnov, Boreskov Institute of Catalysis, Russia
M.O. Hattink, Leiden University, The Netherlands
B.E. Nieuwenhuys, Leiden University, The Netherlands
Correspondent: Click to Email
Oscillations in the NO+H@sub2@ reaction have been observed over the single crystal surfaces of Rh(533), Rh(311), Rh(111) and Pt(100).@footnote 1@ The following N-containing products can be formed: N@sub2@, NH@sub3@ and N@sub2@O. Recently, we observed oscillations over Ir(110)@footnote 2,3@ and Ir(210). The rate of N@sub2@ formation oscillates out of phase with the rate of NH@sub3@ and H@sub2@O formation. No N@sub2@O is formed. By using synchrotron radiation we could perform fast XPS measurements during a heat and cool cycle in the reaction mixture.@footnote 4@ These measurements show that there is a strong repulsive interaction between adsorbed N and O and that N builds-up on the surface during the NH@sub3@ formation. This information was used to propose a model for the oscillations in which the surface oscillates between an N covered surface which blocks the hydrogen adsorption and an O covered surface, which is accessible to hydrogen. A comparable model was suggested for Rh. However, the H@sub2@/NO ratio, the period and the shape of the oscillations are different for these metals. This is probably caused by differences in the rate of the various reactions that take place. The NO+H@sub2@ reaction over Ru(0001) shows a different picture. In this case hardly any NH@sub3@ is formed during a heat and cool cycle even under H-rich conditions and instead of a build-up of N a build-up of O on the surface was obtained. No oscillations have been observed so far. A comparison of the non-linear behaviour in the NO+H@sub2@ reaction of these various metals will be made. @FootnoteText@@footnote 1@N.M.H. Janssen, P.D. Cobden, B.E. Nieuwenhuys, J. Phys.: Condens. Matter 9 (1997) 1889-1917 @footnote 2@C.A.de Wolf, B.E.Nieuwenhuys, A. Sasahara, K.Tanaka, M.M. Slinko, M.Yu. Smirnov, Surf. Sci. 411 (1998) L904-L909 @footnote 3@C.A. de Wolf, B.E. Nieuwenhuys, M.M. Slinko, M.Yu. Smirnov, accepted for publication in the Proc. of IVC-14 to be published in Surface Science @footnote 4@C.A. de Wolf, S. Lizzit, A. Baraldi, M. Kiskinova, B.E. Nieuwenhuys, in preparation.