Nonlinear Dynamics of Complex Surface Reactions

Many environmentally or economically important chemical reactions take place on catalytic surfaces, such as the CO-oxidation on platinum metals in catalytic automotive converters. Most of these reactions exhibit features of nonlinear dynamics systems under certain operating conditions. There are typical pressure and temperature regimes in which for instance chaotic behavior persists. The aim of our first project is to explore, theoretically and experimentally, new directions in controlling and manipulating surface reactions, attempting the "taming of chaos". Continuing with previous research, we plan to study pattern formation in the CO oxidation reaction on platinum under periodic forcing conditions through the gas phase. We will be extending these investigations to composite materials created by microlithography. In addition, we will utilize our focused laser beam to locally manipulate and control reaction patterns on microlithographically modified catalytic surfaces. Another avenue of our research program will utilize ultra thin metal foils as catalysts for studying surface reactions. Due to the heat produced during a chemical reaction these foils buckle and this mechanical deformation can be used as a simple sensor for certain reactants. Ultra thin metal foils will become simple inexpensive "mechanical" instruments for measuring certain types of reaction rates at an unprecedented low budget, requiring minimal equipment and power. This will be explored further with interested industries. Our second research direction is moving towards another practical application, focusing on pitting corrosion. Our technique, Ellipso-Microscopy can now visualize changes of the thickness of the protective oxide layer surrounding metastable pitting events on stainless steels and other alloys. In collaboration with theoreticians, models of such corrosion phenomena will be further developed and analyzed. The aim of these studies will be to find surfactants, which, even in diminutive quantities are capable of suppressing the onset of pitting corrosion, which could be of enormous economical and environmental significance.