SPATIAL COUPLING BETWEEN KINETIC OSCILLATIONS ON DIFFERENT REGIONS OF A CYLINDRICAL PT SINGLE-CRYSTAL

Kinetic oscillations in the catalytic CO oxidation have been investigated in the 10-5 and 10-4 torr range on a cylindrical Pt single crystal whose axis is oriented parallel to the [001]-direction. Two Kelvin probes and measurements of the reaction rate served to follow the local and the integral behavior of kinetic oscillations. The cylindrical surface exhibits the orientations (100), (110) and (210) whose oscillatory behavior has been studied before. The orientational dependence of the existence region for kinetic oscillations was investigated at T = 480 K. A strong broadening of the oscillatory region in parameter space as compared to a flat surface was detected for the (100) orientation which is attributed to coupling effects between different regions of the surface. In the vicinity of the (100) orientations, propagating reaction fronts provide the spatial coupling between different regions, while the (110) orientations communicate via gas phase coupling. Prolonged oscillation experiments cause an increase in catalytic activity around the (110) orientation, whereas the catalytic activity of the (210) orientation decreases. © 1990 Pergamon Press plc.