Kinetic oscillations in oxidation of CO over Pt(100): A study by Rutherford backscattering, nuclear microanalysis, LEED, and work function techniques

The structure and composition of a Pt(100) surface have been monitored by Rutherford backscattering (RBS), nuclear microanalysis (NMA), LEED, and work function (Δφ) techniques during temporal oscillations in the rate of CO oxidation. For a Δφ oscillation amplitude of 60 mV, a constant 0.46±0.06×1015 Pt atoms are out of registry with the bulk throughout an oscillation cycle. The maximum fraction of the surface that could be oscillating between the hex and (1×1) phases is thus 8%. The average CO and O coverages during the oscillations are 0.19±0.04 and 0.13±0.03 monolayers, respectively. These results are discussed in terms of a recent model for the temporal oscillations. No oscillations in Δφ have been detected in similar experiments on Pt(111).