Unusual behaviour of chemical waves in the NO + H2 reaction on Rh(111): long-range diffusion and formation of patches with reduced work function

Janssen, N.M.H.; Schaak, A.; Nieuwenhuys, B.E.; Imbihl, R.

doi:10.1016/0039-6028(96)00793-5

Cited by 42 publications

(26 citation statements)

References 29 publications

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“…Elliptically and rectangularly shaped chemical waves were found with PEEM on Rh͑110͒ and these shapes could be controlled by changing the experimental conditions. 12 The PEEM results reported for Rh͑111͒ 13 are rather similar to those for Rh͑110͒, except that no square waves were observed. A new species was observed, which was characterized by a work function drop below that of the clear surface when two or more reaction fronts collided.…”

Section: Modeled the Oscillations Reported Forsupporting

confidence: 76%

“…This species can be attributed to either subsurface oxygen or NH x . 13 The first observations of rate oscillations and hysteresis phenomena in the NOϩH 2 reaction over macroscopic Rh single crystal surfaces were reported by Janssen et al 14,15 for Rh͑533͒ and recently by Cobden et al 16 for Rh͑111͒. An interesting feature of the oscillatory kinetics in the NOϩH 2 reaction is that, for Pt͑100͒, N 2 and NH 3 signals oscillate in phase, whereas for Rh͑533͒ and Rh͑111͒, the rate of N 2 formation oscillates out of phase with the rate of NH 3 formation.…”

Section: Modeled the Oscillations Reported Formentioning

confidence: 97%

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Kinetic oscillations and hysteresis phenomena in the NO+H2 reaction on Rh(111) and Rh(533): Experiments and mathematical modeling

Makeev

Slinko

Janssen

et al. 1996

The Journal of Chemical Physics

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Interesting kinetic phenomena, such as multiple steady states and kinetic oscillations recently found in the NOϩH 2 reaction over Rh͑533͒ and Rh͑111͒ single crystal surfaces in the 10 Ϫ6 mbar pressure range have been studied by means of experiments and computer modeling. A mathematical model, consisting of five ordinary differential equations and taking into account the lateral interactions in the adlayer, has been developed for simulating the NOϩH 2 /Rh͑533͒ and NOϩH 2 /Rh͑111͒ reactions. The simulation results make it possible to explain in detail the underlying reasons for the experimentally observed complex dynamic behavior. In particular, the kinetic oscillations and their properties have been reproduced. It was found that accumulation of NH ads species, which serves as an intermediate in the pathway of NH 3 production, is an important step in the oscillatory mechanism. In addition, the same mathematical model is able to successfully reproduce the experimental data concerning temperature programmed desorption ͑TPD͒ spectra, hysteresis phenomena, and the dependence of selectivity upon temperature and reactant partial pressures. Lateral interactions in the adlayer are shown to play a crucial role in the adequate simulation of the experimental observations.

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Section: Modeled the Oscillations Reported Forsupporting

confidence: 76%

Section: Modeled the Oscillations Reported Formentioning

confidence: 97%

Kinetic oscillations and hysteresis phenomena in the NO+H2 reaction on Rh(111) and Rh(533): Experiments and mathematical modeling

Makeev

Slinko

Janssen

et al. 1996

The Journal of Chemical Physics

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“…The first of these steps, i.e. the chemisorption of oxygen on Rh single crystal surfaces, has been the subject of intensive experimental and theoretical research, [7][8][9][10] but only few experimental studies have addressed the ensuing formation of sub-surface oxygen, [11][12][13][14][15][16][17] . In one of these studies it could recently be shown 16 that exposure of the Rh(111) surface to O 2 at moderatly elevated temperatures (∼ 470 K) leads to the formation of sub-surface oxygen species, and there is evidence that at least ∼ 0.9 monolayer (ML) of O is adsorbed on the surface before sub-surface sites are occupied.…”

Section: Introductionmentioning

confidence: 99%

Stability of subsurface oxygen at Rh(111)

2002

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Using density-functional theory (DFT) we investigate the incorporation of oxygen directly below the Rh(111) surface. We show that oxygen incorporation will only commence after nearly completion of a dense O adlayer (θtot ≈ 1.0 monolayer) with O in the fcc on-surface sites. The experimentally suggested octahedral sub-surface site occupancy, inducing a site-switch of the onsurface species from fcc to hcp sites, is indeed found to be a rather low energy structure. Our results indicate that at even higher coverages oxygen incorporation is followed by oxygen agglomeration in two-dimensional sub-surface islands directly below the first metal layer. Inside these islands, the metastable hcp/octahedral (on-surface/sub-surface) site combination will undergo a barrierless displacement, introducing a stacking fault of the first metal layer with respect to the underlying substrate and leading to a stable fcc/tetrahedral site occupation. We suggest that these elementary steps, namely, oxygen incorporation, aggregation into sub-surface islands and destabilization of the metal surface may be more general and precede the formation of a surface oxide at close-packed late transition metal surfaces.

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“…setting up the PEEM system by Prof. Schlö gl in Compared with previous results [1][2][3][4][5][6], the formaFritz -Haber-Institut der MPG (Berlin). This tion of subsurface oxygen occurred on the defect work was financially supported by the National surface under a rather low pressure.…”

mentioning

confidence: 83%

“…Pt, Pd, Rh) has been extensively studied. Under Photoemission electron microscopy (PEEM ) is certain conditions, oxygen adsorbed on the surbased on the principle that the photoelectron yield faces can penetrate the topmost layer of the bulk depends sensitively on the local work function to form subsurface oxygen species, which may when the surface is illuminated by an ultraviolet alter the catalytic activities [1][2][3][4][5][6]. For example, light source whose energy is just above the threshsubsurface oxygen is believed to play an important hold of photoelectron exciting [8].…”

mentioning

confidence: 99%