Non-linear behaviour in the NOH2 reaction over Rh(111)

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

“…The hysteresis in the NH 3 formation rate corresponds to the experimental data. 16 As in the experiment, the width of the hysteresis loop becomes smaller with increasing P H2 . As can be seen from Figs.…”

“…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.…”

“…However, the main features of observed oscillations for both catalysts are as follows: [14][15][16] ͑1͒ Oscillatory behavior could be obtained on the cooling branch of the temperature hysteresis. Above a H 2 /NO ratio of about eight some peaks in the N 2 formation rate appear during the cooling period.…”

“…[14][15][16] The shape of the hysteresis loop was demonstrated to vary significantly with the variation of the P NO /P H2 ratio. The results of mathematical modeling for temperature variation using different P NO /P H2 ratios and with P NO kept constant are shown in Fig.…”

“…The complicated changes in the shape of the hysteresis loop are modeled in a good qualitative manner as compared with the experimental data. 16 During the cooling period, the N 2 formation rate displays a local maximum. With increase of the P H2 /P NO ratio this N 2 production peak becomes at first more pronounced and then diminishes in size.…”