Formation of two-dimensional concentration pulses on microdesigned composite catalyst surfaces

We study the effect of microdesigned composite geometries on pattern formation during the catalytic oxidation of CO on Pt-Ti, Pt-Rh, and Pt-Pd composite catalysts. In particular, we find experimentally (and rationalize through modeling) that adsorbate surface transport through the second (active) component drastically affects the shapes and interactions of concentration patterns (traveling pulses) observed on pure Pt. The use, over the last ten years, of spatially resolving techniques such as photoemission electron microscopy (PEEM) [1], and others [2,3], has allowed the real-time, in situ observation of spatiotemporal pattern formation on catalytic surfaces. These observations have important implications for the understanding of the transport and reaction mechanisms underlying catalytic reactions. At the same time, the generic features of the instabilities and bifurcations involved have made catalytic reactions a fruitful model medium for the study of such phenomena, leading to insights for pattern forming systems at large. A recent promising research avenue is the use of microfabrication techniques to construct microreacting domains with controlled shapes and sizes. The boundaries of these domains can be inert: in our case 2000 A “tall” Ti walls, presumably