Kinetic oscillations in the rate of CO oxidation on Pd(110)

Abstract

The oxidation of carbon monoxide on a Pd(110) single crystal plane has been studied using work function changes (Δφ) and mass spectrometric measurements. The rate of reaction showed oscillatory behaviour for oxygen pressures greater than 10 −3 Torr. The existence region for oscillations was determined for pressures ranging from 10 −3 to 1.0 Torr and depended on the pressures of oxygen and carbon monoxide and the sample temperature ( P co, PO 2 T). Transitions from regular oscillation to chaos via period doubling have been observed in certain areas of the existence region. A comparison between Pd(110) and platinum single crystal surfaces that exhibit oscillations showed that similar but not identical oscillatory behaviour and existence regions exist in each case. Our results indicate that oscillations can occur on other metal single crystal surface that are less likely than platinum to reconstruct under reaction conditions. The extension of oscillations from UHV conditions to the 1.0 Torr pressure region indicates that the mechanism responsible for isothermal oscillations is basically independent of the reactant pressure up to several Torr.