Oscillations of the NO-H-2 reaction over Ir(110) in activity and selectivity

Self-sustained isothermal oscillations in the NO-H, reaction were found on the Ir(110) surface. The rates of NH3 and N-2 formation oscillate exactly o ut of phase. The high activity state during the oscillations (high NO conve rsion) corresponds to a high rate of NH3 formation, while in the low activi ty state a high rate of N-2 formation has been observed. The shape of the oscillations is very sensitive to changes in the H-2/NO ra tio or temperature. Build-up of a stable N species might play an important role in the mechanism of the oscillations. (C) 1999 Elsevier Science B.V. A ll rights reserved.