Spatial pattern formation in the NO+CO reaction on a cylindrical Pt single crystal surface (axis parallel [001] direction) has been investigated using photoemission electron microscopy (PEEM) as an in-situ method to image the lateral adsorbate distribution during the reaction with a resolution of ≊1 μm. The experiments were conducted in the 10−6 Torr range, between 380 and 430 K, under conditions where the (100) orientation exhibits oscillatory behavior. Of the different orientations of the [001] zone which are present on the surface only the orientational range between (100) and (310) was found to be very active in NO dissociation and hence in the surface reaction. A sharp phase boundary meandering between (210) and (410) parallel to the [001] direction separates the active from the inactive zone on the cylinder surface. In the active zone between (100) and (310) one finds propagating reaction fronts and complex spatiotemporal patterns. The velocity of the reaction fronts is strongly anisotropic with the maximum occurring in the [001] direction, parallel to the steps on the cylinder surface, while the minimum velocity is observed perpendicular to the step edges. At constant temperature the spatial patterns display turbulent behavior. Due to averaging, these patterns are associated with a stationary reaction rate. Upon a small temperature change of ≊1–3 K the turbulent pattern orders into a target pattern with parallel reaction fronts. Macroscopically, this transition corresponds to the excitation of kinetic oscillations which then decay after a number of cycles as the pattern becomes turbulent again. The occurrence of damped oscillations in the NO+CO reaction on Pt(100) can thus be explained as being due to the absence of an efficient synchronization mode.

Veser, G., & Imbihl, R. (1992). Spatial pattern formation in the oscillatory NO+CO reaction on a Pt(100) surface and its vicinal orientations. The Journal of Chemical Physics, 96(9), 7155–7163.