The oscillating CO oxidation is investigated on a Pt‐field emitter tip by using the field ion mode of surface imaging of Oad sites with O2 as imaging gas. Based on data of the titration reactions [V. Gorodetskii, W. Drachsel, and J. H. Block, J. Chem. Phys. 100, C. E. UPDATE (1994)], external control parameters for the regions of bistability and of self‐sustained isothermal oscillations could be found. On a field emitter tip, oscillations can be generated in a rather large parameter space. The anticlockwise hysteresis of O+2 ion currents in temperature cycles occurs in agreement with results on single crystal planes. Unexpected regular oscillation sequences could occasionally be obtained on the small surface areas of a field emitter tip and measured as function of the CO partial pressure and of the temperature. Different stages within oscillating cycles were documented by field ion images. Oscillations of total ion currents are correlated with variations in the spatial brightness of field ion images. In the manifold of single crystal planes of a field emitter {331} planes around the {011} regions are starting points for oscillations which mainly proceed along [100] vicinals. This excludes the {111} regions from autonomous oscillations. With slightly increased CO partial pressures fast local oscillations at a few hundred surface sites of the Pt(001) plane display short‐living CO islands of 40 to 50 Å diameter. Temporal oscillations of the total O+2 ion current are mainly caused by surface plane specific spatial oscillations. The synchronization is achieved by diffusion reaction fronts rather than by gas phase synchronization.
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1 May 1994
Research Article|
May 01 1994
Field ion microscopic studies of the CO oxidation on platinum: Bistability and oscillations
V. Gorodetskii;
V. Gorodetskii
Fritz‐Haber‐Institut der Max‐Planck‐Gesellschaft Faradayweg 4‐6, Dahlem, D‐14195 Berlin, Germany
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W. Drachsel;
W. Drachsel
Fritz‐Haber‐Institut der Max‐Planck‐Gesellschaft Faradayweg 4‐6, Dahlem, D‐14195 Berlin, Germany
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M. Ehsasi;
M. Ehsasi
Fritz‐Haber‐Institut der Max‐Planck‐Gesellschaft Faradayweg 4‐6, Dahlem, D‐14195 Berlin, Germany
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J. H. Block
J. H. Block
Fritz‐Haber‐Institut der Max‐Planck‐Gesellschaft Faradayweg 4‐6, Dahlem, D‐14195 Berlin, Germany
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J. Chem. Phys. 100, 6915–6922 (1994)
Article history
Received:
August 06 1993
Accepted:
January 06 1994
Citation
V. Gorodetskii, W. Drachsel, M. Ehsasi, J. H. Block; Field ion microscopic studies of the CO oxidation on platinum: Bistability and oscillations. J. Chem. Phys. 1 May 1994; 100 (9): 6915–6922. https://doi.org/10.1063/1.467007
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