A fast x-ray photoelectron spectroscopy study of the NO-H2 reaction over Rh(533): Identifying surface species

Abstract

The behavior of the NO-H 2 reaction over Rh͑533͒ was studied in situ using fast x-ray photoelectron spectroscopy. The high energy resolution achieved by using synchrotron light allowed us to distinguish five surface species by analyzing the line shape and energy positions of the N 1s and O 1s photoelectron spectra. It was established that there are three nitrogen species, labeled NO, N͑I͒ and N͑II͒. The species NO and N͑I͒ are attributed to adsorbed NO and atomic nitrogen, respectively. The nitrogen species N͑II͒ might be attributed to atomic nitrogen adsorbed at step sites or to an NH x species. The short measurement time for the spectra opens the possibility of studying the reaction more dynamically.

Surface science studies of selective catalytic reduction of NO: Progress in the last ten years

“…However, due to its relatively simpler reaction pathway (in the authors' opinion), in the past decade, surface science studies of this reaction have not been so actively pursued as those of the NO-CO and NO-NH 3 reactions, and the studies which have been carried out mainly focus on its dynamical behavior, i.e., the well-known oscillation phenomena . Nieuwenhuys's group has taken a leading role in this field, having a series of publications related to their studies on various surfaces, including Pt, Rh, Pd, Ir and Ru [107][108][109][110][111][112][113][114][115][116][117][118][119][120]. No oscillations in rate have been observed over Pd(1 1 1) and Ru(0 0 0 1).…”

Evidence of repulsive interactions between NO, O, and N on Ir(110). A fast x-ray photoelectron spectroscopy study

“…12 This technique was already successfully applied to the understanding of the nonlinear behavior of the NO-H 2 reaction over Rh͑533͒. 13,14 The NO/Ir͑110͒ system has previously been studied by Ibbotson et al 15 From these studies it was concluded that NO adsorbs molecularly up to room temperature. Furthermore, heating a NO saturated surface leads to some desorption of NO around 400 K, creating vacancies needed for NO dissociation which results in N 2 desorption around 430 K. Finally, both NO and N 2 desorb above 450 K, from which the conclusion was drawn that oxygen overlayers tend to stabilize NO with respect to dissociation and desorption.…”

Nonlinear Behavior in the NO−H2Reaction over Ir(110) Studied by Fast X-ray Photoelectron Spectroscopy

“…The feature with a binding energy of −397.90 eV can be attributed to atomic N, and the peak at a binding energy of −401.20 eV can be correlated to molecular NO, just as in Figure . The third component, fixed at −398.98 eV, was also observed for the same reaction over Rh(533) and was thought to originate either from a NH x species or atomic N adsorbed on the step sites. , To check the probability of a NH x species, uptake experiments were carried out for NH 3 at various temperatures. It appeared that a fitting component, that could be attributed to a NH x species, had the same binding energy as the third N species in the heating−cooling cycles at R = 25.…”

“…The evolution of the species present on the surface during the heating−cooling cycle for the NO−H 2 reaction over Ir(110) is very similar to the ones that were observed for the same reaction over Rh(533), except for the third N species which is not present for the reactions at low H 2 /NO ratios over Ir(110). This N species was attributed to N adsorbed on the step sites or a NH x species, although it was also observed during the uptake of NO over Rh(533). , Besides, over rhodium, the third N species was destabilized by atomic N and its formation was promoted by O ads , whereas in the case of Ir(110), this third N species is formed only during the formation of NH 3 and it shares the surface with atomic N. This might suggest that these N species have a different origin. In a later paper by these authors on the uptake of NO over Rh(533), Rh(311), and Rh(111) studied by fast-XPS, this third N species was assigned to N ads on step sites because it appeared to be absent on Rh(111) .…”

“…Recently, fast X-ray photoelectron spectroscopy was successfully used to study the NO−H 2 reaction over Rh(533). , During a heating−cooling cycle three different N-containing species and two O-containing species were observed. These species were attributed to molecular NO and atomic N and O and the third N species was attributed to either a NH x species or atomic N adsorbed on the step sites.…”