Spatiotemporal patterns during CO oxidation on Pt(100) at elevated pressures

() CO oxidation on Pt 100 was inestigated at reactant pressures of 8 Pa using ellip- somicroscopy for surface imaging to monitor spatiotemporal pattern formation on the catalyst surface and mass spectroscopy to monitor the integral reaction rate. Three dis- tinct temperature regions showing nonlinear phenomena were found. The first region, at 540 ) 615 K, is characterized by macroscopic, regular reaction-rate oscillations with spa- tially uniform, instantaneous transitions between CO and oxygen coered states. Regu- () lar, periodic oscillations were not obsered on Pt 100 before. The second region, 480 ) 540 K, exhibited continuous dynamic pattern formation with noisible macro- scopic kinetic oscillations. Front speeds measured indicated a decrease in oxygen front ¤elocity and an increase in CO frontelocity with an increasing COrO partial pressure 2 ratio. The third region, 390 ) 430 K, is characterized by macroscopic rate oscillations, which continued for seeral oscillation periods and then ceased with the onset of pattern formation.

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